build: set $GOPATH/bin as default GOBIN for Config.BinPath

We should avoid making any changes to GOROOT whenever possible.

Fixes #361

Update internal/build/build.go

Co-authored-by: 张之阳 <[email protected]>

internal/build/build.go

@@ -18,6 +18,7 @@ package build
 
 import (
 	"archive/zip"
+	"errors"
 	"fmt"
 	"go/constant"
 	"go/token"
@@ -70,7 +71,11 @@ type Config struct {
 func NewDefaultConf(mode Mode) *Config {
 	bin := os.Getenv("GOBIN")
 	if bin == "" {
-		bin = filepath.Join(runtime.GOROOT(), "bin")
+		gopath, err := envGOPATH()
+		if err != nil {
+			panic(fmt.Errorf("cannot get GOPATH: %v", err))
+		}
+		bin = filepath.Join(gopath, "bin")
 	}
 	conf := &Config{
 		BinPath: bin,
@@ -80,6 +85,28 @@ func NewDefaultConf(mode Mode) *Config {
 	return conf
 }
 
+func envGOPATH() (string, error) {
+	if gopath := os.Getenv("GOPATH"); gopath != "" {
+		return gopath, nil
+	}
+	env := "HOME"
+	switch runtime.GOOS {
+	case "windows":
+		env = "USERPROFILE"
+	case "plan9":
+		env = "home"
+	}
+	home := os.Getenv(env)
+	if home == "" {
+		return "", fmt.Errorf("%s is not set", env)
+	}
+	def := filepath.Join(home, "go")
+	if filepath.Clean(def) == filepath.Clean(runtime.GOROOT()) {
+		return "", errors.New("cannot set GOROOT as GOPATH")
+	}
+	return def, nil
+}
+
 func DefaultAppExt() string {
 	if runtime.GOOS == "windows" {
 		return ".exe"