Update go to 1.15

Currently DC/OS CLI keeps backward compatibility for macOS 10.10 Yosemite (2014) after updating Go version we will drop it and support only macOS 10.12 Sierra or later.

It's now the industry standard to deprecate TLS 1.0 and 1.1.
See: https://tools.ietf.org/html/draft-ietf-tls-oldversions-deprecate-00

Refs: dcos/dcos-cli#1552

.appveyor.yml

@@ -1,6 +1,6 @@
 install:
   - SET PATH=C:\msys64\mingw64\bin;c:\gopath\bin;%PATH%
-  - curl -sfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh| sh -s -- -b "c:\gopath\bin" v1.24.0
+  - curl -sfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh| sh -s -- -b "c:\gopath\bin" v1.30.0
 
 build: off
 
@@ -11,7 +11,8 @@ environment:
   NO_DOCKER: 1
   GO111MODULE: off
 
-stack: go 1.12
+stack: go 1.15
+image: Visual Studio 2019
 
 test_script:
   - SET GO111MODULE=on

.travis.yml

@@ -4,15 +4,15 @@ os:
 
 language: go
 
-go: "1.12.x"
+go: "1.15.x"
 
 go_import_path: github.com/dcos/dcos-core-cli
 
 env:
  - NO_DOCKER=1 GO111MODULE=on
 
 before_install:
- - curl -sfL https://install.goreleaser.com/github.com/golangci/golangci-lint.sh | sh -s -- -b $(go env GOPATH)/bin v1.24.0
+ - curl -sfL https://install.goreleaser.com/github.com/golangci/golangci-lint.sh | sh -s -- -b $(go env GOPATH)/bin v1.30.0
 
 script:
  - make

Dockerfile

@@ -1,3 +1,3 @@
-FROM golang:1.12
+FROM golang:1.15
 
-RUN curl -sfL https://install.goreleaser.com/github.com/golangci/golangci-lint.sh | sh -s -- -b $(go env GOPATH)/bin v1.24.0
+RUN curl -sfL https://install.goreleaser.com/github.com/golangci/golangci-lint.sh | sh -s -- -b $(go env GOPATH)/bin v1.30.0

pkg/cmd/pkg/package_install_test.go

@@ -25,5 +25,5 @@ func TestPkgInstallEmptyPackageNameShouldFail(t *testing.T) {
 func TestPkgInstallShouldFailOnCosmosError(t *testing.T) {
 	ctx := mock.NewContext(nil)
 	err := pkgInstall(ctx, "helloworld", pkgInstallOptions{})
-	assert.EqualError(t, err, `Post /package/describe: unsupported protocol scheme ""`)
+	assert.EqualError(t, err, `Post "/package/describe": unsupported protocol scheme ""`)
 }

pkg/pluginutil/pluginutil.go

@@ -43,7 +43,7 @@ func HTTPClient(baseURL string, opts ...httpclient.Option) *httpclient.Client {
 			if err == nil {
 				certPool := x509.NewCertPool()
 				if certPool.AppendCertsFromPEM(rootCAsPEM) {
-					baseOpts = append(baseOpts, httpclient.TLS(&tls.Config{RootCAs: certPool}))
+					baseOpts = append(baseOpts, httpclient.TLS(&tls.Config{RootCAs: certPool, MinVersion: tls.VersionTLS12}))
 				}
 			}
 		}