diff --git a/buildcache.go b/buildcache.go
index 4b6c63ab..44b2340a 100644
--- a/buildcache.go
+++ b/buildcache.go
@@ -5,16 +5,9 @@ import (
 	"os"
 	"path/filepath"
 	"time"
-)
 
-// Get the cache directory, usually ~/.cache/tinygo
-func cacheDir() string {
-	dir, err := os.UserCacheDir()
-	if err != nil {
-		panic("could not find cache dir: " + err.Error())
-	}
-	return filepath.Join(dir, "tinygo")
-}
+	"github.com/tinygo-org/tinygo/goenv"
+)
 
 // Return the newest timestamp of all the file paths passed in. Used to check
 // for stale caches.
@@ -41,8 +34,7 @@ func cacheTimestamp(paths []string) (time.Time, error) {
 // TODO: the configKey is currently ignored. It is supposed to be used as extra
 // data for the cache key, like the compiler version and arguments.
 func cacheLoad(name, configKey string, sourceFiles []string) (string, error) {
-	dir := cacheDir()
-	cachepath := filepath.Join(dir, name)
+	cachepath := filepath.Join(goenv.Get("GOCACHE"), name)
 	cacheStat, err := os.Stat(cachepath)
 	if os.IsNotExist(err) {
 		return "", nil // does not exist
@@ -76,7 +68,7 @@ func cacheStore(tmppath, name, configKey string, sourceFiles []string) (string,
 
 	// TODO: check the config key
 
-	dir := cacheDir()
+	dir := goenv.Get("GOCACHE")
 	err := os.MkdirAll(dir, 0777)
 	if err != nil {
 		return "", err
diff --git a/builtins.go b/builtins.go
index 8ac127f7..15b94b66 100644
--- a/builtins.go
+++ b/builtins.go
@@ -10,6 +10,7 @@ import (
 	"time"
 
 	"github.com/blakesmith/ar"
+	"github.com/tinygo-org/tinygo/goenv"
 )
 
 // These are the GENERIC_SOURCES according to CMakeList.txt.
@@ -169,13 +170,13 @@ func builtinFiles(target string) []string {
 
 // builtinsDir returns the directory where the sources for compiler-rt are kept.
 func builtinsDir() string {
-	return filepath.Join(sourceDir(), "lib", "compiler-rt", "lib", "builtins")
+	return filepath.Join(goenv.Get("TINYGOROOT"), "lib", "compiler-rt", "lib", "builtins")
 }
 
 // Get the builtins archive, possibly generating it as needed.
 func loadBuiltins(target string) (path string, err error) {
 	// Try to load a precompiled compiler-rt library.
-	precompiledPath := filepath.Join(sourceDir(), "pkg", target, "compiler-rt.a")
+	precompiledPath := filepath.Join(goenv.Get("TINYGOROOT"), "pkg", target, "compiler-rt.a")
 	if _, err := os.Stat(precompiledPath); err == nil {
 		// Found a precompiled compiler-rt for this OS/architecture. Return the
 		// path directly.
diff --git a/goenv/goenv.go b/goenv/goenv.go
new file mode 100644
index 00000000..c02d35df
--- /dev/null
+++ b/goenv/goenv.go
@@ -0,0 +1,189 @@
+// Package goenv returns environment variables that are used in various parts of
+// the compiler. You can query it manually with the `tinygo env` subcommand.
+package goenv
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"os/user"
+	"path/filepath"
+	"runtime"
+)
+
+// Keys is a slice of all available environment variable keys.
+var Keys = []string{
+	"GOOS",
+	"GOARCH",
+	"GOROOT",
+	"GOPATH",
+	"GOCACHE",
+	"TINYGOROOT",
+}
+
+// TINYGOROOT is the path to the final location for checking tinygo files. If
+// unset (by a -X ldflag), then sourceDir() will fallback to the original build
+// directory.
+var TINYGOROOT string
+
+// Get returns a single environment variable, possibly calculating it on-demand.
+// The empty string is returned for unknown environment variables.
+func Get(name string) string {
+	switch name {
+	case "GOOS":
+		if dir := os.Getenv("GOOS"); dir != "" {
+			return dir
+		}
+		return runtime.GOOS
+	case "GOARCH":
+		if dir := os.Getenv("GOARCH"); dir != "" {
+			return dir
+		}
+		return runtime.GOARCH
+	case "GOROOT":
+		return getGoroot()
+	case "GOPATH":
+		if dir := os.Getenv("GOPATH"); dir != "" {
+			return dir
+		}
+
+		// fallback
+		home := getHomeDir()
+		return filepath.Join(home, "go")
+	case "GOCACHE":
+		// Get the cache directory, usually ~/.cache/tinygo
+		dir, err := os.UserCacheDir()
+		if err != nil {
+			panic("could not find cache dir: " + err.Error())
+		}
+		return filepath.Join(dir, "tinygo")
+	case "TINYGOROOT":
+		return sourceDir()
+	default:
+		return ""
+	}
+}
+
+// Return the TINYGOROOT, or exit with an error.
+func sourceDir() string {
+	// Use $TINYGOROOT as root, if available.
+	root := os.Getenv("TINYGOROOT")
+	if root != "" {
+		if !isSourceDir(root) {
+			fmt.Fprintln(os.Stderr, "error: $TINYGOROOT was not set to the correct root")
+			os.Exit(1)
+		}
+		return root
+	}
+
+	if TINYGOROOT != "" {
+		if !isSourceDir(TINYGOROOT) {
+			fmt.Fprintln(os.Stderr, "error: TINYGOROOT was not set to the correct root")
+			os.Exit(1)
+		}
+		return TINYGOROOT
+	}
+
+	// Find root from executable path.
+	path, err := os.Executable()
+	if err != nil {
+		// Very unlikely. Bail out if it happens.
+		panic("could not get executable path: " + err.Error())
+	}
+	root = filepath.Dir(filepath.Dir(path))
+	if isSourceDir(root) {
+		return root
+	}
+
+	// Fallback: use the original directory from where it was built
+	// https://stackoverflow.com/a/32163888/559350
+	_, path, _, _ = runtime.Caller(0)
+	root = filepath.Dir(filepath.Dir(path))
+	if isSourceDir(root) {
+		return root
+	}
+
+	fmt.Fprintln(os.Stderr, "error: could not autodetect root directory, set the TINYGOROOT environment variable to override")
+	os.Exit(1)
+	panic("unreachable")
+}
+
+// isSourceDir returns true if the directory looks like a TinyGo source directory.
+func isSourceDir(root string) bool {
+	_, err := os.Stat(filepath.Join(root, "src/runtime/internal/sys/zversion.go"))
+	if err != nil {
+		return false
+	}
+	_, err = os.Stat(filepath.Join(root, "src/device/arm/arm.go"))
+	return err == nil
+}
+
+func getHomeDir() string {
+	u, err := user.Current()
+	if err != nil {
+		panic("cannot get current user: " + err.Error())
+	}
+	if u.HomeDir == "" {
+		// This is very unlikely, so panic here.
+		// Not the nicest solution, however.
+		panic("could not find home directory")
+	}
+	return u.HomeDir
+}
+
+// getGoroot returns an appropriate GOROOT from various sources. If it can't be
+// found, it returns an empty string.
+func getGoroot() string {
+	goroot := os.Getenv("GOROOT")
+	if goroot != "" {
+		// An explicitly set GOROOT always has preference.
+		return goroot
+	}
+
+	// Check for the location of the 'go' binary and base GOROOT on that.
+	binpath, err := exec.LookPath("go")
+	if err == nil {
+		binpath, err = filepath.EvalSymlinks(binpath)
+		if err == nil {
+			goroot := filepath.Dir(filepath.Dir(binpath))
+			if isGoroot(goroot) {
+				return goroot
+			}
+		}
+	}
+
+	// Check what GOROOT was at compile time.
+	if isGoroot(runtime.GOROOT()) {
+		return runtime.GOROOT()
+	}
+
+	// Check for some standard locations, as a last resort.
+	var candidates []string
+	switch runtime.GOOS {
+	case "linux":
+		candidates = []string{
+			"/usr/local/go", // manually installed
+			"/usr/lib/go",   // from the distribution
+		}
+	case "darwin":
+		candidates = []string{
+			"/usr/local/go",             // manually installed
+			"/usr/local/opt/go/libexec", // from Homebrew
+		}
+	}
+
+	for _, candidate := range candidates {
+		if isGoroot(candidate) {
+			return candidate
+		}
+	}
+
+	// Can't find GOROOT...
+	return ""
+}
+
+// isGoroot checks whether the given path looks like a GOROOT.
+func isGoroot(goroot string) bool {
+	_, err := os.Stat(filepath.Join(goroot, "src", "runtime", "internal", "sys", "zversion.go"))
+	return err == nil
+}
diff --git a/linker-builtin.go b/linker-builtin.go
index f11d5686..a9872e4b 100644
--- a/linker-builtin.go
+++ b/linker-builtin.go
@@ -9,6 +9,8 @@ import (
 	"os"
 	"os/exec"
 	"unsafe"
+
+	"github.com/tinygo-org/tinygo/goenv"
 )
 
 /*
@@ -63,7 +65,7 @@ func Link(linker string, flags ...string) error {
 		cmd := exec.Command(linker, flags...)
 		cmd.Stdout = os.Stdout
 		cmd.Stderr = os.Stderr
-		cmd.Dir = sourceDir()
+		cmd.Dir = goenv.Get("TINYGOROOT")
 		return cmd.Run()
 	}
 }
diff --git a/linker-external.go b/linker-external.go
index f114b39b..082b3e54 100644
--- a/linker-external.go
+++ b/linker-external.go
@@ -8,6 +8,8 @@ package main
 import (
 	"os"
 	"os/exec"
+
+	"github.com/tinygo-org/tinygo/goenv"
 )
 
 // Link invokes a linker with the given name and arguments.
@@ -20,6 +22,6 @@ func Link(linker string, flags ...string) error {
 	cmd := exec.Command(linker, flags...)
 	cmd.Stdout = os.Stdout
 	cmd.Stderr = os.Stderr
-	cmd.Dir = sourceDir()
+	cmd.Dir = goenv.Get("TINYGOROOT")
 	return cmd.Run()
 }
diff --git a/main.go b/main.go
index 120a5a91..aa621470 100644
--- a/main.go
+++ b/main.go
@@ -18,6 +18,7 @@ import (
 	"time"
 
 	"github.com/tinygo-org/tinygo/compiler"
+	"github.com/tinygo-org/tinygo/goenv"
 	"github.com/tinygo-org/tinygo/interp"
 	"github.com/tinygo-org/tinygo/loader"
 
@@ -70,7 +71,7 @@ func Compile(pkgName, outpath string, spec *TargetSpec, config *BuildConfig, act
 		config.gc = spec.GC
 	}
 
-	root := sourceDir()
+	root := goenv.Get("TINYGOROOT")
 
 	// Merge and adjust CFlags.
 	cflags := append([]string{}, config.cFlags...)
@@ -84,7 +85,7 @@ func Compile(pkgName, outpath string, spec *TargetSpec, config *BuildConfig, act
 		ldflags = append(ldflags, strings.Replace(flag, "{root}", root, -1))
 	}
 
-	goroot := getGoroot()
+	goroot := goenv.Get("GOROOT")
 	if goroot == "" {
 		return errors.New("cannot locate $GOROOT, please set it manually")
 	}
@@ -123,7 +124,7 @@ func Compile(pkgName, outpath string, spec *TargetSpec, config *BuildConfig, act
 		VerifyIR:      config.verifyIR,
 		TINYGOROOT:    root,
 		GOROOT:        goroot,
-		GOPATH:        getGopath(),
+		GOPATH:        goenv.Get("GOPATH"),
 		BuildTags:     tags,
 		TestConfig:    config.testConfig,
 	}
@@ -454,7 +455,7 @@ func Flash(pkgName, target, port string, config *BuildConfig) error {
 			cmd := exec.Command("/bin/sh", "-c", flashCmd)
 			cmd.Stdout = os.Stdout
 			cmd.Stderr = os.Stderr
-			cmd.Dir = sourceDir()
+			cmd.Dir = goenv.Get("TINYGOROOT")
 			err := cmd.Run()
 			if err != nil {
 				return &commandError{"failed to flash", tmppath, err}
@@ -719,7 +720,7 @@ func usage() {
 	fmt.Fprintln(os.Stderr, "  test:  test packages")
 	fmt.Fprintln(os.Stderr, "  flash: compile and flash to the device")
 	fmt.Fprintln(os.Stderr, "  gdb:   run/flash and immediately enter GDB")
-	fmt.Fprintln(os.Stderr, "  clean: empty cache directory ("+cacheDir()+")")
+	fmt.Fprintln(os.Stderr, "  clean: empty cache directory ("+goenv.Get("GOCACHE")+")")
 	fmt.Fprintln(os.Stderr, "  help:  print this help text")
 	fmt.Fprintln(os.Stderr, "\nflags:")
 	flag.PrintDefaults()
@@ -890,8 +891,7 @@ func main() {
 		handleCompilerError(err)
 	case "clean":
 		// remove cache directory
-		dir := cacheDir()
-		err := os.RemoveAll(dir)
+		err := os.RemoveAll(goenv.Get("GOCACHE"))
 		if err != nil {
 			fmt.Fprintln(os.Stderr, "cannot clean cache:", err)
 			os.Exit(1)
diff --git a/target.go b/target.go
index 25e9ff8d..92b4b564 100644
--- a/target.go
+++ b/target.go
@@ -8,17 +8,13 @@ import (
 	"io/ioutil"
 	"os"
 	"os/exec"
-	"os/user"
 	"path/filepath"
 	"regexp"
 	"runtime"
 	"strings"
-)
 
-// TINYGOROOT is the path to the final location for checking tinygo files. If
-// unset (by a -X ldflag), then sourceDir() will fallback to the original build
-// directory.
-var TINYGOROOT string
+	"github.com/tinygo-org/tinygo/goenv"
+)
 
 // Target specification for a given target. Used for bare metal targets.
 //
@@ -147,7 +143,7 @@ func (spec *TargetSpec) loadFromGivenStr(str string) error {
 	if strings.HasSuffix(str, ".json") {
 		path, _ = filepath.Abs(str)
 	} else {
-		path = filepath.Join(sourceDir(), "targets", strings.ToLower(str)+".json")
+		path = filepath.Join(goenv.Get("TINYGOROOT"), "targets", strings.ToLower(str)+".json")
 	}
 	fp, err := os.Open(path)
 	if err != nil {
@@ -186,14 +182,8 @@ func LoadTarget(target string) (*TargetSpec, error) {
 	if target == "" {
 		// Configure based on GOOS/GOARCH environment variables (falling back to
 		// runtime.GOOS/runtime.GOARCH), and generate a LLVM target based on it.
-		goos := os.Getenv("GOOS")
-		if goos == "" {
-			goos = runtime.GOOS
-		}
-		goarch := os.Getenv("GOARCH")
-		if goarch == "" {
-			goarch = runtime.GOARCH
-		}
+		goos := goenv.Get("GOOS")
+		goarch := goenv.Get("GOARCH")
 		llvmos := goos
 		llvmarch := map[string]string{
 			"386":   "i386",
@@ -315,141 +305,6 @@ func (spec *TargetSpec) OpenOCDConfiguration() (args []string, err error) {
 	return args, nil
 }
 
-// Return the TINYGOROOT, or exit with an error.
-func sourceDir() string {
-	// Use $TINYGOROOT as root, if available.
-	root := os.Getenv("TINYGOROOT")
-	if root != "" {
-		if !isSourceDir(root) {
-			fmt.Fprintln(os.Stderr, "error: $TINYGOROOT was not set to the correct root")
-			os.Exit(1)
-		}
-		return root
-	}
-
-	if TINYGOROOT != "" {
-		if !isSourceDir(TINYGOROOT) {
-			fmt.Fprintln(os.Stderr, "error: TINYGOROOT was not set to the correct root")
-			os.Exit(1)
-		}
-		return TINYGOROOT
-	}
-
-	// Find root from executable path.
-	path, err := os.Executable()
-	if err != nil {
-		// Very unlikely. Bail out if it happens.
-		panic("could not get executable path: " + err.Error())
-	}
-	root = filepath.Dir(filepath.Dir(path))
-	if isSourceDir(root) {
-		return root
-	}
-
-	// Fallback: use the original directory from where it was built
-	// https://stackoverflow.com/a/32163888/559350
-	_, path, _, _ = runtime.Caller(0)
-	root = filepath.Dir(path)
-	if isSourceDir(root) {
-		return root
-	}
-
-	fmt.Fprintln(os.Stderr, "error: could not autodetect root directory, set the TINYGOROOT environment variable to override")
-	os.Exit(1)
-	panic("unreachable")
-}
-
-// isSourceDir returns true if the directory looks like a TinyGo source directory.
-func isSourceDir(root string) bool {
-	_, err := os.Stat(filepath.Join(root, "src/runtime/internal/sys/zversion.go"))
-	if err != nil {
-		return false
-	}
-	_, err = os.Stat(filepath.Join(root, "src/device/arm/arm.go"))
-	return err == nil
-}
-
-func getGopath() string {
-	gopath := os.Getenv("GOPATH")
-	if gopath != "" {
-		return gopath
-	}
-
-	// fallback
-	home := getHomeDir()
-	return filepath.Join(home, "go")
-}
-
-func getHomeDir() string {
-	u, err := user.Current()
-	if err != nil {
-		panic("cannot get current user: " + err.Error())
-	}
-	if u.HomeDir == "" {
-		// This is very unlikely, so panic here.
-		// Not the nicest solution, however.
-		panic("could not find home directory")
-	}
-	return u.HomeDir
-}
-
-// getGoroot returns an appropriate GOROOT from various sources. If it can't be
-// found, it returns an empty string.
-func getGoroot() string {
-	goroot := os.Getenv("GOROOT")
-	if goroot != "" {
-		// An explicitly set GOROOT always has preference.
-		return goroot
-	}
-
-	// Check for the location of the 'go' binary and base GOROOT on that.
-	binpath, err := exec.LookPath("go")
-	if err == nil {
-		binpath, err = filepath.EvalSymlinks(binpath)
-		if err == nil {
-			goroot := filepath.Dir(filepath.Dir(binpath))
-			if isGoroot(goroot) {
-				return goroot
-			}
-		}
-	}
-
-	// Check what GOROOT was at compile time.
-	if isGoroot(runtime.GOROOT()) {
-		return runtime.GOROOT()
-	}
-
-	// Check for some standard locations, as a last resort.
-	var candidates []string
-	switch runtime.GOOS {
-	case "linux":
-		candidates = []string{
-			"/usr/local/go", // manually installed
-			"/usr/lib/go",   // from the distribution
-		}
-	case "darwin":
-		candidates = []string{
-			"/usr/local/go",             // manually installed
-			"/usr/local/opt/go/libexec", // from Homebrew
-		}
-	}
-
-	for _, candidate := range candidates {
-		if isGoroot(candidate) {
-			return candidate
-		}
-	}
-
-	// Can't find GOROOT...
-	return ""
-}
-
-// isGoroot checks whether the given path looks like a GOROOT.
-func isGoroot(goroot string) bool {
-	_, err := os.Stat(filepath.Join(goroot, "src", "runtime", "internal", "sys", "zversion.go"))
-	return err == nil
-}
-
 // getGorootVersion returns the major and minor version for a given GOROOT path.
 // If the goroot cannot be determined, (0, 0) is returned.
 func getGorootVersion(goroot string) (major, minor int, err error) {