dev-doctor: use default GOPATH when missing from env

Signed-off-by: Alexandre Perrin <alex@kaworu.ch>

tools/dev-doctor/common.go

@@ -3,7 +3,11 @@
 
 package main
 
-import "os/exec"
+import (
+	"go/build"
+	"os"
+	"os/exec"
+)
 
 // sudo returns cmd run with sudo. cmd is modified in place.
 func sudo(cmd *exec.Cmd) (*exec.Cmd, error) {
@@ -15,3 +19,11 @@ func sudo(cmd *exec.Cmd) (*exec.Cmd, error) {
 	cmd.Path = sudoPath
 	return cmd, nil
 }
+
+// goPath returns the environment $GOPATH, or the default when empty or unset.
+func goPath() string {
+	if gp := os.Getenv("GOPATH"); gp != "" {
+		return gp
+	}
+	return build.Default.GOPATH
+}

tools/dev-doctor/rootcmd.go

@@ -40,7 +40,7 @@ func rootCmdRun(cmd *cobra.Command, args []string) {
 		osArchCheck{},
 		unameCheck{},
 		rootDirCheck{
-			rootDir: "$GOPATH/src/github.com/cilium/cilium",
+			rootDir: goPath() + "/src/github.com/cilium/cilium",
 		},
 		&binaryCheck{
 			name:          "make",

tools/dev-doctor/rootdircheck.go

@@ -23,11 +23,6 @@ func (c rootDirCheck) Name() string {
 }
 
 func (c rootDirCheck) Run() (checkResult, string) {
-	goPath := os.Getenv("GOPATH")
-	if goPath == "" {
-		return checkWarning, "$GOPATH is not set"
-	}
-
 	dir, err := os.Getwd()
 	if err != nil {
 		return checkError, fmt.Sprintf("cannot get working directory: %s", err)
@@ -40,8 +35,8 @@ func (c rootDirCheck) Run() (checkResult, string) {
 		case err == nil && info.Mode().IsDir():
 			if dir != os.ExpandEnv(c.rootDir) {
 				foundDir := dir
-				if strings.HasPrefix(dir, goPath+"/") {
-					foundDir = "$GOPATH/" + dir[len(goPath)+1:]
+				if strings.HasPrefix(dir, goPath()+"/") {
+					foundDir = "$GOPATH/" + dir[len(goPath())+1:]
 				}
 				return checkWarning, fmt.Sprintf("found %s, want %s", foundDir, c.rootDir)
 			}