switch to Go API v2 for protobuf

seems that sticking to Go API v1 for protobuf is headache for projects
using GoBGP.

This breaks the compatibility so bumps up the major version to 3.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>

.github/workflows/ci.yml

@@ -29,11 +29,14 @@ jobs:
     runs-on: ubuntu-18.04
     steps:
       - uses: actions/checkout@master
+      - uses: actions/setup-go@v2
+        with:
+          go-version: '^1.17.4'
       - run: |
           test -z "$(go fmt ./...)"
           go vet ./...
           export PATH=${PATH}:`go env GOPATH`/bin
-          go get -u honnef.co/go/tools/cmd/staticcheck
+          go install honnef.co/go/tools/cmd/staticcheck@2021.1.2
           staticcheck ./...
 
   embeded: