Fix a typo syscanll.SIGTERM -> syscall.SIGTERM (gin-gonic#1868)

Author: DeathKing

README.md

@@ -1696,9 +1696,9 @@ func main() {
 	// Wait for interrupt signal to gracefully shutdown the server with
 	// a timeout of 5 seconds.
 	quit := make(chan os.Signal)
-	// kill (no param) default send syscanll.SIGTERM
+	// kill (no param) default send syscall.SIGTERM
 	// kill -2 is syscall.SIGINT
-	// kill -9 is syscall. SIGKILL but can"t be catch, so don't need add it
+	// kill -9 is syscall.SIGKILL but can"t be catch, so don't need add it
 	signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)
 	<-quit
 	log.Println("Shutdown Server ...")