update Dockerfile and .circleci/config.yml

.circleci/config.yml

@@ -2,7 +2,7 @@ version: 2
 jobs:
   build:
     docker:
-      - image: circleci/golang:1.15
+      - image: circleci/golang:1.16
     working_directory: ~/twhelpapi
     steps:
       - checkout
@@ -25,4 +25,4 @@ workflows:
           filters:
             branches:
               only:
-                - master
+                - master

Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:alpine as builder
+FROM golang as builder
 
 # Set the Current Working Directory inside the container
 WORKDIR /app