Bump go.mod and docker go version to 1.16 (#18280)

* Bump go.mod go version to 1.16

* Bump docker build go version to 1.16.7

build/Dockerfile.buildenv

@@ -1,3 +1,3 @@
-FROM golang:1.15.5
+FROM golang:1.16.7
 
 RUN apt-get update && apt-get install -y make git apt-transport-https ca-certificates curl software-properties-common build-essential zip xmlsec1 jq