refactor: remove mutex from CustomEvent and update TCP connection handling in tests

common/custom-event.go

@@ -9,7 +9,6 @@ import (
 	"io"
 	"net/http"
 	"strings"
-	"sync"
 )
 
 type stringWriter interface {
@@ -48,13 +47,13 @@ var dataReplacer = strings.NewReplacer(
 	"\n", "\n",
 	"\r", "\\r")
 
+// CustomEvent does not synchronize writes to the response writer. Streaming
+// callers must serialize event writes at the stream level.
 type CustomEvent struct {
 	Event string
 	Id    string
 	Retry uint
 	Data  interface{}
-
-	Mutex sync.Mutex
 }
 
 func encode(writer io.Writer, event CustomEvent) error {
@@ -76,8 +75,6 @@ func (r CustomEvent) Render(w http.ResponseWriter) error {
 }
 
 func (r CustomEvent) WriteContentType(w http.ResponseWriter) {
-	r.Mutex.Lock()
-	defer r.Mutex.Unlock()
 	header := w.Header()
 	header["Content-Type"] = writeContentType
 

common/email_test.go

@@ -364,7 +364,7 @@ func TestSMTPPlainAuthRejectsRemotePlaintextConnection(t *testing.T) {
 	SMTPFrom = "sender@example.com"
 	SMTPToken = "secret"
 
-	conn, err := net.Dial("tcp", fmt.Sprintf("%s:%d", server.host, server.port))
+	conn, err := net.Dial("tcp", net.JoinHostPort(server.host, strconv.Itoa(server.port)))
 	require.NoError(t, err)
 	client, err := smtp.NewClient(conn, SMTPServer)
 	require.NoError(t, err)