upgrade to go1.20 and remove useless generate files (daixiang0#141)

Signed-off-by: Loong <long0dai@foxmail.com>

Makefile

@@ -1,8 +1,8 @@
-.PHONY: clean generate test build
+.PHONY: clean test build
 
 BIN_OUTPUT := $(if $(filter $(shell go env GOOS), windows), dist/gci.exe, dist/gci)
 
-default: clean generate test build
+default: clean test build
 
 clean:
 	@echo BIN_OUTPUT: ${BIN_OUTPUT}
@@ -13,6 +13,3 @@ build: clean
 
 test: clean
 	@go test -v -count=1 -cover ./...
-
-generate:
-	@go generate ./...

go.mod

@@ -1,26 +1,24 @@
 module github.com/daixiang0/gci
 
-go 1.18
+go 1.20
 
 require (
 	github.com/hexops/gotextdiff v1.0.3
-	github.com/spf13/cobra v1.3.0
-	github.com/stretchr/testify v1.8.0
-	go.uber.org/zap v1.17.0
-	golang.org/x/sync v0.0.0-20210220032951-036812b2e83c
-	golang.org/x/tools v0.1.5
+	github.com/spf13/cobra v1.6.1
+	github.com/stretchr/testify v1.8.1
+	go.uber.org/zap v1.24.0
+	golang.org/x/sync v0.1.0
+	golang.org/x/tools v0.6.0
 	gopkg.in/yaml.v3 v3.0.1
 )
 
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
-	github.com/inconshreveable/mousetrap v1.0.0 // indirect
-	github.com/pkg/errors v0.9.1 // indirect
+	github.com/inconshreveable/mousetrap v1.0.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/spf13/pflag v1.0.5 // indirect
 	go.uber.org/atomic v1.7.0 // indirect
 	go.uber.org/multierr v1.6.0 // indirect
-	golang.org/x/mod v0.5.0 // indirect
-	golang.org/x/sys v0.0.0-20211216021012-1d35b9e2eb4e // indirect
-	golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 // indirect
+	golang.org/x/mod v0.8.0 // indirect
+	golang.org/x/sys v0.5.0 // indirect
 )