Fail with better error messages if go binary cannot be found

src/goInstallTools.ts

@@ -292,6 +292,9 @@ export function updateGoPathGoRootFromConfig(): Promise<void> {
 
 	// If GOPATH is still not set, then use the one from `go env`
 	let goRuntimePath = getGoRuntimePath();
+	if (!goRuntimePath) {
+		return Promise.reject(new Error('Cannot find "go" binary. Update PATH or GOROOT appropriately'));
+	}
 	return new Promise<void>((resolve, reject) => {
 		cp.execFile(goRuntimePath, ['env', 'GOPATH'], (err, stdout, stderr) => {
 			if (err) {

src/util.ts

@@ -562,7 +562,16 @@ export interface ICheckResult {
  */
 export function runTool(args: string[], cwd: string, severity: string, useStdErr: boolean, toolName: string, env: any, printUnexpectedOutput: boolean, token?: vscode.CancellationToken): Promise<ICheckResult[]> {
 	let goRuntimePath = getGoRuntimePath();
-	let cmd = toolName ? getBinPath(toolName) : goRuntimePath;
+	let cmd;
+	if (toolName) {
+		cmd = getBinPath(toolName);
+	} else {
+		if (!goRuntimePath) {
+			return Promise.reject(new Error('Cannot find "go" binary. Update PATH or GOROOT appropriately'));
+		}
+		cmd = goRuntimePath;
+	}
+
 	let p: cp.ChildProcess;
 	if (token) {
 		token.onCancellationRequested(() => {