automatically get latest k3s version tag at build time

Makefile

@@ -10,13 +10,16 @@ ifeq ($(GIT_TAG),)
 GIT_TAG   := $(shell git describe --always)
 endif
 
+# get latest k3s version
+K3S_TAG		:= $(shell curl --silent "https://api.github.com/repos/rancher/k3s/releases/latest" | grep '"tag_name":' | sed -E 's/.*"([^"]+)".*/\1/')
+
 # Go options
 GO        ?= go
 PKG       := $(shell go mod vendor)
 TAGS      :=
 TESTS     := .
 TESTFLAGS :=
-LDFLAGS   := -w -s -X github.com/rancher/k3d/version.Version=${GIT_TAG}
+LDFLAGS   := -w -s -X github.com/rancher/k3d/version.Version=${GIT_TAG} -X github.com/rancher/k3d/version.K3sVersion=${K3S_TAG}
 GOFLAGS   :=
 BINDIR    := $(CURDIR)/bin
 BINARIES  := k3d

main.go

@@ -57,7 +57,7 @@ func main() {
 				},
 				cli.StringFlag{
 					Name:  "version",
-					Value: "v0.4.0",
+					Value: version.GetK3sVersion(),
 					Usage: "Choose the k3s image version",
 				},
 				cli.IntFlag{

version/version.go

@@ -3,6 +3,9 @@ package version
 // Version is the string that contains version
 var Version string
 
+// K3sVersion contains the latest version tag of K3s
+var K3sVersion string
+
 // GetVersion returns the version for cli, it gets it from "git describe --tags" or returns "dev" when doing simple go build
 func GetVersion() string {
 	if len(Version) == 0 {
@@ -10,3 +13,8 @@ func GetVersion() string {
 	}
 	return Version
 }
+
+// GetK3sVersion returns the version string for K3s
+func GetK3sVersion() string {
+	return K3sVersion
+}