Fix IPv6 url without 80/443 port (#1636)

This PR fixes another use case when no port is passed to a IPv6 with
brackets hostname.

Use url.URL.Hostname() since it strips the port and the brackets from
the hostname as well.

Add more unit tests to getEndpointURL() as well.

utils.go

@@ -161,27 +161,18 @@ func isValidEndpointURL(endpointURL url.URL) error {
 	if endpointURL.Path != "/" && endpointURL.Path != "" {
 		return errInvalidArgument("Endpoint url cannot have fully qualified paths.")
 	}
-
-	host, _, err := net.SplitHostPort(endpointURL.Host)
-	if err != nil {
-		if strings.Contains(err.Error(), "missing port in address") {
-			err = nil
-			host = endpointURL.Host
-		} else {
-			return err
-		}
-	}
+	host := endpointURL.Hostname()
 	if !s3utils.IsValidIP(host) && !s3utils.IsValidDomain(host) {
 		msg := "Endpoint: " + endpointURL.Host + " does not follow ip address or domain name standards."
 		return errInvalidArgument(msg)
 	}
 
-	if strings.Contains(endpointURL.Host, ".s3.amazonaws.com") {
+	if strings.Contains(host, ".s3.amazonaws.com") {
 		if !s3utils.IsAmazonEndpoint(endpointURL) {
 			return errInvalidArgument("Amazon S3 endpoint should be 's3.amazonaws.com'.")
 		}
 	}
-	if strings.Contains(endpointURL.Host, ".googleapis.com") {
+	if strings.Contains(host, ".googleapis.com") {
 		if !s3utils.IsGoogleEndpoint(endpointURL) {
 			return errInvalidArgument("Google Cloud Storage endpoint should be 'storage.googleapis.com'.")
 		}

utils_test.go

@@ -113,6 +113,12 @@ func TestGetEndpointURL(t *testing.T) {
 		{"192.168.1.1:9000", false, "http://192.168.1.1:9000", nil, true},
 		{"192.168.1.1:9000", true, "https://192.168.1.1:9000", nil, true},
 		{"s3.amazonaws.com:443", true, "https://s3.amazonaws.com:443", nil, true},
+		{"[::1]", false, "http://[::1]", nil, true},
+		{"[::1]", true, "https://[::1]", nil, true},
+		{"[::1]:80", false, "http://[::1]:80", nil, true},
+		{"[::1]:443", true, "https://[::1]:443", nil, true},
+		{"[::1]:9000", false, "http://[::1]:9000", nil, true},
+		{"[::1]:9000", true, "https://[::1]:9000", nil, true},
 		{"13333.123123.-", true, "", errInvalidArgument(fmt.Sprintf("Endpoint: %s does not follow ip address or domain name standards.", "13333.123123.-")), false},
 		{"13333.123123.-", true, "", errInvalidArgument(fmt.Sprintf("Endpoint: %s does not follow ip address or domain name standards.", "13333.123123.-")), false},
 		{"storage.googleapis.com:4000", true, "", errInvalidArgument("Google Cloud Storage endpoint should be 'storage.googleapis.com'."), false},