build: use GOPROXY and disable download on some steps (#7745)

* build: use GOPROXY

* disable download vendor on some steps

.drone.yml

     image: golang:1.11 # this step is kept as the lowest version of golang that we support
     environment:
       GO111MODULE: on
+      GOPROXY: off
     commands:
       - go build -mod=vendor -o gitea_no_gcc # test if build succeeds without the sqlite tag
 
     image: golang:1.12
     environment:
       GO111MODULE: on
+      GOPROXY: off
       GOOS: linux
       GOARCH: 386
     commands:
       - make test-vendor
       - make build
     environment:
+      GOPROXY: https://goproxy.cn # proxy.golang.org is blocked in China, this proxy is not
       TAGS: bindata sqlite sqlite_unlock_notify
 
   - name: unit-test
     commands:
       - make unit-test-coverage
     environment:
+      GOPROXY: off
       TAGS: bindata sqlite sqlite_unlock_notify
     depends_on:
       - build
     commands:
       - make test
     environment:
+      GOPROXY: off
       TAGS: bindata sqlite sqlite_unlock_notify
     depends_on:
       - build
     commands:
       - make test
     environment:
+      GOPROXY: off
       TAGS: bindata
     depends_on:
       - tag-pre-condition
       - timeout -s ABRT 20m make test-sqlite-migration
       - timeout -s ABRT 20m make test-sqlite
     environment:
+      GOPROXY: off
       TAGS: bindata
     depends_on:
       - build
       - make test-mysql-migration
       - make integration-test-coverage
     environment:
+      GOPROXY: off
       TAGS: bindata
       TEST_LDAP: 1
     depends_on:
       - timeout -s ABRT 20m make test-mysql-migration
       - timeout -s ABRT 20m make test-mysql
     environment:
+      GOPROXY: off
       TAGS: bindata
       TEST_LDAP: 1
     depends_on:
       - timeout -s ABRT 20m make test-mysql8-migration
       - timeout -s ABRT 20m make test-mysql8
     environment:
+      GOPROXY: off
       TAGS: bindata
       TEST_LDAP: 1
     depends_on:
       - timeout -s ABRT 20m make test-pgsql-migration
       - timeout -s ABRT 20m make test-pgsql
     environment:
+      GOPROXY: off
       TAGS: bindata
       TEST_LDAP: 1
     depends_on:
       - make test-mssql-migration
       - make test-mssql
     environment:
+      GOPROXY: off
       TAGS: bindata
       TEST_LDAP: 1
     depends_on:
     commands:
       - make coverage
     environment:
+      GOPROXY: off
       TAGS: bindata
     depends_on:
       - unit-test
       - make generate
       - make release
     environment:
+      GOPROXY: off
       TAGS: bindata sqlite sqlite_unlock_notify
 
   - name: gpg-sign
       - make generate
       - make release
     environment:
+      GOPROXY: off
       TAGS: bindata sqlite sqlite_unlock_notify
 
   - name: gpg-sign
       dry_run: true
       repo: gitea/gitea
       tags: linux-amd64
+      build_args:
+        - GOPROXY=off
     when:
       event:
         - pull_request
       auto_tag: true
       auto_tag_suffix: linux-amd64
       repo: gitea/gitea
+      build_args:
+        - GOPROXY=off
       password:
         from_secret: docker_password
       username:
       dry_run: true
       repo: gitea/gitea
       tags: linux-arm64
+      build_args:
+        - GOPROXY=off
     when:
       event:
         - pull_request
       auto_tag: true
       auto_tag_suffix: linux-arm64
       repo: gitea/gitea
+      build_args:
+        - GOPROXY=off
       password:
         from_secret: docker_password
       username:

Dockerfile

 #Build stage
 FROM golang:1.12-alpine3.10 AS build-env
 
+ARG GOPROXY
+ENV GOPROXY ${GOPROXY:-direct}
+
 ARG GITEA_VERSION
 ARG TAGS="sqlite sqlite_unlock_notify"
 ENV TAGS "bindata $TAGS"