diff --git a/src/cmd/go/internal/cache/default.go b/src/cmd/go/internal/cache/default.go
index 02fc1e896f..4a69bf2a44 100644
--- a/src/cmd/go/internal/cache/default.go
+++ b/src/cmd/go/internal/cache/default.go
@@ -9,7 +9,6 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
-	"runtime"
 	"sync"
 )
 
@@ -78,52 +77,19 @@ func defaultDir() (string, bool) {
 	}
 
 	// Compute default location.
-	// TODO(rsc): This code belongs somewhere else,
-	// like maybe ioutil.CacheDir or os.CacheDir.
-	showWarnings := true
-	switch runtime.GOOS {
-	case "windows":
-		dir = os.Getenv("LocalAppData")
-		if dir == "" {
-			// Fall back to %AppData%, the old name of
-			// %LocalAppData% on Windows XP.
-			dir = os.Getenv("AppData")
-		}
-		if dir == "" {
-			return "off", true
-		}
-
-	case "darwin":
-		dir = os.Getenv("HOME")
-		if dir == "" {
-			return "off", true
-		}
-		dir += "/Library/Caches"
-
-	case "plan9":
-		dir = os.Getenv("home")
-		if dir == "" {
-			return "off", true
-		}
-		// Plan 9 has no established per-user cache directory,
-		// but $home/lib/xyz is the usual equivalent of $HOME/.xyz on Unix.
-		dir += "/lib/cache"
-
-	default: // Unix
-		// https://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html
-		dir = os.Getenv("XDG_CACHE_HOME")
-		if dir == "" {
-			dir = os.Getenv("HOME")
-			if dir == "" {
-				return "off", true
-			}
-			if dir == "/" {
-				// probably docker run with -u flag
-				// https://golang.org/issue/26280
-				showWarnings = false
-			}
-			dir += "/.cache"
-		}
+	dir, err := os.UserCacheDir()
+	if err != nil {
+		return "off", true
 	}
-	return filepath.Join(dir, "go-build"), showWarnings
+	dir = filepath.Join(dir, "go-build")
+
+	// Do this after filepath.Join, so that the path has been cleaned.
+	showWarnings := true
+	switch dir {
+	case "/.cache/go-build":
+		// probably docker run with -u flag
+		// https://golang.org/issue/26280
+		showWarnings = false
+	}
+	return dir, showWarnings
 }