README: clarify when flag defaults are used (#78)

* README: clarify when flag defaults are used

* go.mod: somewhat pointless bump to go 1.16

* Make GitHub Actions happy

.github/workflows/test.yml

@@ -4,7 +4,7 @@ jobs:
   test:
     strategy:
       matrix:
-        go-version: [1.13.x]
+        go-version: [1.16.x]
         platform: [ubuntu-latest, macos-latest, windows-latest]
     runs-on: ${{ matrix.platform }}
     steps:
@@ -13,28 +13,25 @@ jobs:
       with:
         go-version: ${{ matrix.go-version }}
     - name: Install staticcheck
-      run: pwd && cd .. && go get -v -u honnef.co/go/tools/cmd/staticcheck && cd -
+      run: go install honnef.co/go/tools/cmd/staticcheck@latest
       shell: bash
     - name: Install golint
-      run: pwd && cd .. && go get -v -u golang.org/x/lint/golint && cd -
+      run: go install golang.org/x/lint/golint@latest
       shell: bash
     - name: Update PATH
-      # https://github.com/actions/setup-go/issues/12#issuecomment-524631719
-      run: echo "##[add-path]$(go env GOPATH)/bin" 
+      run: echo "$(go env GOPATH)/bin" >> $GITHUB_PATH
       shell: bash
     - name: Checkout code
       uses: actions/checkout@v1
     - name: Fmt
       if: matrix.platform != 'windows-latest' # :(
-      run: "F=$(gofmt -l .) ; if [[ $F ]] ; then echo $F ; exit 1 ; fi"
+      run: "diff <(gofmt -d .) <(printf '')"
       shell: bash
     - name: Vet
       run: go vet ./...
     - name: Staticcheck
       run: staticcheck ./...
     - name: Lint
       run: golint ./...
-    - name: Parallel tests
-      run: hack/lint-parallel-tests.bash
     - name: Test
       run: go test -race ./...

README.md

@@ -46,7 +46,9 @@ are available to control parse behavior.
 ```
 
 This example will parse flags from the commandline args, just like regular
-package flag, with the highest priority.
+package flag, with the highest priority. (The flag's default value will be used
+only if the flag remains unset after parsing all provided sources of
+configuration.)
 
 Additionally, the example will look in the environment for variables with a
 `MY_PROGRAM` prefix. Flag names are capitalized, and separator characters are
@@ -56,6 +58,7 @@ would match to `listen-addr`.
 Finally, if a `-config` file is specified, the example will try to parse it
 using the PlainParser, which expects files in this format.
 
+
 ```
 listen-addr localhost:8080
 refresh 30s

go.mod

@@ -1,6 +1,6 @@
 module github.com/peterbourgon/ff/v3
 
-go 1.14
+go 1.16
 
 require (
 	github.com/pelletier/go-toml v1.6.0