Update Golang 1.13.8

Also pinning the e2e image to the "buster" variant,
which is what's currently used, but making it explicit.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

appveyor.yml

@@ -4,7 +4,7 @@ clone_folder: c:\gopath\src\github.com\docker\cli
 
 environment:
   GOPATH: c:\gopath
-  GOVERSION: 1.12.17
+  GOVERSION: 1.13.8
   DEPVERSION: v0.4.1
 
 install:

dockerfiles/Dockerfile.binary-native

@@ -1,4 +1,4 @@
-ARG GO_VERSION=1.12.17
+ARG GO_VERSION=1.13.8
 
 FROM    golang:${GO_VERSION}-alpine
 

dockerfiles/Dockerfile.cross

@@ -1,4 +1,4 @@
-ARG GO_VERSION=1.12.17
+ARG GO_VERSION=1.13.8
 
 FROM	dockercore/golang-cross:${GO_VERSION}
 ENV     DISABLE_WARN_OUTSIDE_CONTAINER=1

dockerfiles/Dockerfile.dev

@@ -1,4 +1,4 @@
-ARG GO_VERSION=1.12.17
+ARG GO_VERSION=1.13.8
 
 FROM    golang:${GO_VERSION}-alpine
 

dockerfiles/Dockerfile.e2e

@@ -1,7 +1,7 @@
-ARG GO_VERSION=1.12.17
+ARG GO_VERSION=1.13.8
 
 # Use Debian based image as docker-compose requires glibc.
-FROM golang:${GO_VERSION}
+FROM golang:${GO_VERSION}-buster
 
 RUN apt-get update && apt-get install -y \
     build-essential \

dockerfiles/Dockerfile.lint

@@ -1,6 +1,6 @@
 # syntax=docker/dockerfile:1.1.3-experimental
 
-ARG GO_VERSION=1.12.17
+ARG GO_VERSION=1.13.8
 ARG GOLANGCI_LINTER_SHA="v1.21.0"
 
 FROM    golang:${GO_VERSION}-alpine AS build