Dockerfile: build docker images on go 1.20

Dockerfile

@@ -1,6 +1,6 @@
 # Builder image
 # Keep go version in sync with Build GA job.
-FROM golang:1.18-alpine as builder
+FROM golang:1.20-alpine as builder
 
 # Display go version for information purposes.
 RUN go version

Dockerfile.wsc

@@ -43,14 +43,14 @@ RUN $newPath = ('{0}\bin;C:\Program Files\Go\bin;{1}' -f $env:GOPATH, $env:PATH)
  	[Environment]::SetEnvironmentVariable('PATH', $newPath, [EnvironmentVariableTarget]::Machine);
 
 # Keep go version in sync with Build GA job.
-ENV GOLANG_VERSION=1.19
+ENV GOLANG_VERSION=1.20
 
-RUN $url = 'https://go.dev/dl/go1.19.windows-amd64.zip'; \
+RUN $url = 'https://go.dev/dl/go1.20.windows-amd64.zip'; \
  	Write-Host ('Downloading {0} ...' -f $url); \
  	[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12; \
  	Invoke-WebRequest -Uri $url -OutFile 'go.zip'; \
  	\
-    $sha256 = 'bcaaf966f91980d35ae93c37a8fe890e4ddfca19448c0d9f66c027d287e2823a'; \
+    $sha256 = 'e8f6d8bbcf3df58d2ba29818e13b04c2e42ba2e4d90d580720b21c34d10bbf68'; \
  	Write-Host ('Verifying sha256 ({0}) ...' -f $sha256); \
  	if ((Get-FileHash go.zip -Algorithm sha256).Hash -ne $sha256) { \
  	    Write-Host 'FAILED!'; \