chore: Go 1.17 released

- run tests on Go 1.17
- Go 1.15 no longer in support

Author: blgm

.github/workflows/test.yml

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        version: [ '1.16' ]
+        version: [ '1.16', '1.17' ]
     name: Go ${{ matrix.version }}
     steps:
     - uses: actions/setup-go@v2

go.mod

@@ -1,6 +1,6 @@
 module github.com/onsi/ginkgo
 
-go 1.15
+go 1.16
 
 require (
 	github.com/go-task/slim-sprig v0.0.0-20210107165309-348f09dbbbc0