CI: Test with Go 1.17 (#287)

Go 1.17 was released today. Test against it.

Go 1.17 includes a new format for specifying `// +build` constraints
`//go:build`. To aid in migrating to it, `gofmt` syncs these two.

.github/workflows/go.yml

@@ -13,9 +13,9 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go: ["1.15.x", "1.16.x"]
+        go: ["1.15.x", "1.16.x", "1.17.x"]
         include:
-        - go: 1.16.x
+        - go: 1.17.x
           latest: true
 
     steps:

dig_go19_test.go

@@ -18,6 +18,7 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.
 
+//go:build go1.9
 // +build go1.9
 
 package dig

tools_test.go

@@ -18,6 +18,7 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.
 
+//go:build tools
 // +build tools
 
 package dig

utils_for_go19_test.go

@@ -18,6 +18,7 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.
 
+//go:build go1.9
 // +build go1.9
 
 package dig

utils_for_pre_go19_test.go

@@ -18,6 +18,7 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.
 
+//go:build !go1.9
 // +build !go1.9
 
 package dig