Makefile: Add lint target and factor the check target

Makefile

@@ -31,10 +31,20 @@ PKG_GOLANGCI_LINT := github.com/golangci/golangci-lint/cmd/golangci-lint
 
 export GO111MODULE=on
 
-# go source files, ignore vendor directory
-SRC =  *.go cli/*.go
+# go source directories.
+# DIRS defines a single level directly, we only look at *.go in this directory.
+# REC_DIRS defines a source code tree. All go files are analyzed recursively.
+DIRS :=  .
+REC_DIRS := cli
 
-.PHONY: all build build-cross clean fmt simplify check extra-clean install-tools
+# Rules for finding all go source files using 'DIRS' and 'REC_DIRS'
+GO_SRC := $(foreach dir,$(DIRS),$(wildcard $(dir)/*.go))
+GO_SRC += $(foreach dir,$(REC_DIRS),$(shell find $(dir) -name "*.go"))
+
+# Rules for directory list as input for the golangci-lint program
+LINT_DIRS := $(DIRS) $(foreach dir,$(REC_DIRS),$(dir)/...)
+
+.PHONY: all build build-cross clean fmt check-fmt lint check extra-clean install-tools
 
 all: clean fmt check build
 
@@ -52,13 +62,18 @@ extra-clean: clean
 	go clean -i $(PKG_GOX)
 	go clean -i $(PKG_GOLANGCI_LINT)
 
+# fmt will fix the golang source style in place.
 fmt:
-	@gofmt -s -l -w $(SRC)
+	@gofmt -s -l -w $(GO_SRC)
+
+# check-fmt returns an error code if any source code contains format error.
+check-fmt:
+	@test -z $(shell gofmt -s -l $(GO_SRC) | tee /dev/stderr) || echo "[WARN] Fix formatting issues with 'make fmt'"
+
+lint:
+	@golangci-lint run $(LINT_DIRS)
 
-check:
-	@test -z $(shell gofmt -l main.go | tee /dev/stderr) || echo "[WARN] Fix formatting issues with 'make fmt'"
-	@golangci-lint run
-	@go vet  main.go
+check: check-fmt lint
 
 # Check for required executables
 HAS_GOX := $(shell command -v gox 2> /dev/null)

cli/container.go

@@ -199,7 +199,7 @@ func removeContainer(ID string) error {
 
 	options := types.ContainerRemoveOptions{
 		RemoveVolumes: true,
-		Force:true,
+		Force:         true,
 	}
 
 	if err := docker.ContainerRemove(ctx, ID, options); err != nil {