go.mod,go.sum: bump go version 1.13 -> 1.21 #20

	name: Go

	on:
	push:
	branches: [ master ]
	pull_request:
	branches: [ master ]

	jobs:

	build:
	name: Build
	runs-on: ubuntu-latest
	steps:

	- name: Set up Go 1.x
	uses: actions/setup-go@v2
	with:
	go-version: ^1.13
	id: go

	- name: Check out code into the Go module directory
	uses: actions/checkout@v2

	- name: Get dependencies
	run: \|
	go get -v -t -d ./...

	- name: Build
	run: go build -v .

	- name: Test
	run: go test -v .

Provide feedback