Minor improvements

client/client.go

@@ -3,7 +3,7 @@ package client
 import (
 	"crypto/tls"
 	"crypto/x509"
-	"fmt"
+	"errors"
 	"net"
 	"net/http"
 	"net/smtp"
@@ -78,34 +78,29 @@ func CanCreateTCPConnection(address string) bool {
 	return true
 }
 
-func CanPerformStartTls(address string, insecure bool) (connected bool, certificate *x509.Certificate, err error) {
-	tokens := strings.Split(address, ":")
-	if len(tokens) != 2 {
-		err = fmt.Errorf("invalid address for starttls, must HOST:PORT")
+// CanPerformStartTLS checks whether a connection can be established to an address using the STARTTLS protocol
+func CanPerformStartTLS(address string, insecure bool) (connected bool, certificate *x509.Certificate, err error) {
+	hostAndPort := strings.Split(address, ":")
+	if len(hostAndPort) != 2 {
+		return false, nil, errors.New("invalid address for starttls, format must be host:port")
+	}
+	smtpClient, err := smtp.Dial(address)
+	if err != nil {
 		return
 	}
-	tlsconfig := &tls.Config{
+	err = smtpClient.StartTLS(&tls.Config{
 		InsecureSkipVerify: insecure,
-		ServerName:         tokens[0],
-	}
-
-	c, err := smtp.Dial(address)
+		ServerName:         hostAndPort[0],
+	})
 	if err != nil {
 		return
 	}
-
-	err = c.StartTLS(tlsconfig)
-	if err != nil {
-		return
-	}
-	if state, ok := c.TLSConnectionState(); ok {
+	if state, ok := smtpClient.TLSConnectionState(); ok {
 		certificate = state.PeerCertificates[0]
 	} else {
-		err = fmt.Errorf("could not get TLS connection state")
-		return
+		return false, nil, errors.New("could not get TLS connection state")
 	}
-	connected = true
-	return
+	return true, certificate, nil
 }
 
 // Ping checks if an address can be pinged and returns the round-trip time if the address can be pinged

client/client_test.go

@@ -1,7 +1,6 @@
 package client
 
 import (
-	"crypto/x509"
 	"testing"
 	"time"
 )
@@ -51,35 +50,32 @@ func TestPing(t *testing.T) {
 	}
 }
 
-func TestCanPerformStartTls(t *testing.T) {
+func TestCanPerformStartTLS(t *testing.T) {
 	type args struct {
 		address  string
 		insecure bool
 	}
 	tests := []struct {
-		name            string
-		args            args
-		wantConnected   bool
-		wantCertificate *x509.Certificate
-		wantErr         bool
+		name          string
+		args          args
+		wantConnected bool
+		wantErr       bool
 	}{
 		{
 			name: "invalid address",
 			args: args{
 				address: "test",
 			},
-			wantConnected:   false,
-			wantCertificate: nil,
-			wantErr:         true,
+			wantConnected: false,
+			wantErr:       true,
 		},
 		{
 			name: "error dial",
 			args: args{
 				address: "test:1234",
 			},
-			wantConnected:   false,
-			wantCertificate: nil,
-			wantErr:         true,
+			wantConnected: false,
+			wantErr:       true,
 		},
 		{
 			name: "valid starttls",
@@ -92,13 +88,13 @@ func TestCanPerformStartTls(t *testing.T) {
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			gotConnected, _, err := CanPerformStartTls(tt.args.address, tt.args.insecure)
+			connected, _, err := CanPerformStartTLS(tt.args.address, tt.args.insecure)
 			if (err != nil) != tt.wantErr {
-				t.Errorf("CanPerformStartTls() error = %v, wantErr %v", err, tt.wantErr)
+				t.Errorf("CanPerformStartTLS() err=%v, wantErr=%v", err, tt.wantErr)
 				return
 			}
-			if gotConnected != tt.wantConnected {
-				t.Errorf("CanPerformStartTls() gotConnected = %v, want %v", gotConnected, tt.wantConnected)
+			if connected != tt.wantConnected {
+				t.Errorf("CanPerformStartTLS() connected=%v, wantConnected=%v", connected, tt.wantConnected)
 			}
 		})
 	}