add Go 1.21, drop 1.19

.github/workflows/test.yml

@@ -4,7 +4,7 @@ jobs:
   test:
     strategy:
       matrix:
-        go-version: [1.19.x, 1.20.x]
+        go-version: [1.20.x, 1.21.x]
         os: [ubuntu-latest, macos-latest, windows-latest]
     runs-on: ${{ matrix.os }}
     steps:
@@ -17,7 +17,7 @@ jobs:
 
     # Static checks from this point forward. Only run on one Go version and on
     # Linux, since it's the fastest platform, and the tools behave the same.
-    - if: matrix.os == 'ubuntu-latest' && matrix.go-version == '1.20.x'
+    - if: matrix.os == 'ubuntu-latest' && matrix.go-version == '1.21.x'
       run: diff <(echo -n) <(gofmt -s -d .)
-    - if: matrix.os == 'ubuntu-latest' && matrix.go-version == '1.20.x'
+    - if: matrix.os == 'ubuntu-latest' && matrix.go-version == '1.21.x'
       run: go vet ./...

README.md

@@ -7,15 +7,15 @@
 Enforce a stricter format than `gofmt`, while being backwards compatible.
 That is, `gofumpt` is happy with a subset of the formats that `gofmt` is happy with.
 
-The tool is a fork of `gofmt` as of Go 1.20, and requires Go 1.19 or later.
+The tool is a fork of `gofmt` as of Go 1.21, and requires Go 1.20 or later.
 It can be used as a drop-in replacement to format your Go code,
 and running `gofmt` after `gofumpt` should produce no changes.
 For example:
 
 	gofumpt -l -w .
 
 Some of the Go source files in this repository belong to the Go project.
-The project includes copies of `go/printer` and `go/doc/comment` as of Go 1.20
+The project includes copies of `go/printer` and `go/doc/comment` as of Go 1.21
 to ensure consistent formatting independent of what Go version is being used.
 The [added formatting rules](#Added-rules) are implemented in the `format` package.
 

go.mod

@@ -1,6 +1,6 @@
 module mvdan.cc/gofumpt
 
-go 1.19
+go 1.20
 
 require (
 	github.com/frankban/quicktest v1.14.5