Opened PR: Contributing Docs need an update based on error logs

[shashank-g172]

Describe the bug While attempting to build the container locally while adding a new feature, I noticed that that the contributing.md doc needs an update to a later version of go, but I'm not sure how that'll break Travis builds.

To Reproduce Run the steps on the docs once exec'd into the container

Expected behavior No build errors

** docker info ** Command> go vet ./... output of the command: /root/go/pkg/mod/github.com/containerd/[email protected]/errdefs/errors.go:92:9: undefined: "github.com/pkg/errors".Is

github.com/testcontainers/testcontainers-go/wait

wait/http.go:154:3: unknown field 'ForceAttemptHTTP2' in struct literal of type http.Transport wait/http.go:185:16: undefined: http.NewRequestWithContext note: module requires Go 1.13# github.com/docker/docker/pkg/archive /root/go/pkg/mod/github.com/docker/[email protected]+incompatible/pkg/archive/archive_linux.go:155:18: undefined: strings.ReplaceAll /root/go/pkg/mod/github.com/docker/[email protected]+incompatible/pkg/archive/archive_linux.go:242:18: undefined: strings.ReplaceAll

github.com/testcontainers/testcontainers-go/wait [github.com/testcontainers/testcontainers-go/wait.test]

wait/http.go:154:3: unknown field 'ForceAttemptHTTP2' in struct literal of type http.Transport wait/http.go:185:16: undefined: http.NewRequestWithContext

$ docker info
docker --version
Docker version 18.06.1-ce, build e68fc7a

Additional context