Fix error handling when server fails to start

Also make the ClientRaw.Close method more robust.

client.go

@@ -106,7 +106,7 @@ func StartClientRaw(opts ClientRawOptions) (*ClientRaw, error) {
 	}
 
 	if err := conn.Start(); err != nil {
-		return nil, fmt.Errorf("failed start server: %s: %s", err, conn.stdErr.String())
+		return nil, fmt.Errorf("failed to start server: %s: %s", err, conn.stdErr.String())
 	}
 
 	if opts.OnMessage == nil {
@@ -152,10 +152,22 @@ type ClientRaw struct {
 
 // Close closes the server connection and waits for the server process to quit.
 func (c *ClientRaw) Close() error {
-	if err := c.conn.Close(); err != nil {
-		return c.addErrContext("close", err)
+	if c == nil {
+		return nil
 	}
-	return nil
+	c.sendMu.Lock()
+	defer c.sendMu.Unlock()
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if c.closing {
+		return ErrShutdown
+	}
+	c.closing = true
+
+	err := c.conn.Close()
+
+	return err
 }
 
 // Execute sends body to the server and returns the Message it receives.

client_test.go

@@ -33,6 +33,21 @@ func TestExecRaw(t *testing.T) {
 		c.Assert(err, qt.IsNil)
 		c.Assert(string(result.Body), qt.Equals, "echo: hello")
 	})
+}
+
+func TestExecStartFailed(t *testing.T) {
+	c := qt.New(t)
+	client, err := execrpc.StartClientRaw(
+		execrpc.ClientRawOptions{
+			Version: 1,
+			Cmd:     "go",
+			Dir:     "./examples/servers/doesnotexist",
+			Args:    []string{"run", "."},
+		})
+
+	c.Assert(err, qt.IsNotNil)
+	c.Assert(err.Error(), qt.Contains, "failed to start server: chdir ./examples/servers/doesnotexist")
+	c.Assert(client.Close(), qt.IsNil)
 
 }
 

conn.go

@@ -75,7 +75,7 @@ func (c conn) Close() error {
 func (c conn) Start() error {
 	err := c.cmd.Start()
 	if err != nil {
-		return c.Close()
+		return err
 	}
 
 	ctx, cancel := context.WithTimeout(context.Background(), c.timeout)