add some versions you can install

internal/cmd/list.go

@@ -4,18 +4,89 @@ import (
 	"fmt"
 	"os"
 
+	"github.com/Masterminds/semver"
 	"github.com/urfave/cli/v2"
 )
 
+type versionRange struct {
+	minVerson semver.Version
+	maxVerson semver.Version
+}
+
+var goVersion map[string][]string = map[string][]string{
+	"1.18": {
+		"1.18.1",
+		"1.18",
+	},
+	"1.17": {
+		"1.17.9",
+		"1.17.8",
+		"1.17.7",
+		"1.17.6",
+		"1.17.5",
+		"1.17.4",
+		"1.17.3",
+		"1.17.2",
+		"1.17.1",
+		"1.17",
+	},
+	"1.16": {
+		"1.16.15",
+		"1.16.14",
+		"1.16.13",
+		"1.16.12",
+		"1.16.11",
+		"1.16.10",
+		"1.16.9",
+		"1.16.8",
+		"1.16.7",
+		"1.16.6",
+		"1.16.5",
+		"1.16.4",
+		"1.16.3",
+		"1.16.2",
+		"1.16.1",
+		"1.16",
+	},
+	"1.15": {
+		"1.15.15",
+		"1.15.14",
+		"1.15.13",
+		"1.15.12",
+		"1.15.11",
+		"1.15.10",
+		"1.15.9",
+		"1.15.8",
+		"1.15.7",
+		"1.15.6",
+		"1.15.5",
+		"1.15.4",
+		"1.15.3",
+		"1.15.2",
+		"1.15.1",
+		"1.15",
+	},
+}
+
 func ListCommand(c *cli.Context) error {
 	versions, err := os.ReadDir(InstallDirectory)
 	if err != nil {
 		return err
 	}
 
+	if c.Bool("available") {
+		fmt.Println("Installed Versions:")
+	}
 	for _, version := range versions {
 		fmt.Println(version.Name())
 	}
 
+	if c.Bool("available") {
+		fmt.Println("Available Versions:")
+		for k, v := range goVersion {
+			fmt.Printf("%s: %v\n", k, v)
+		}
+	}
+
 	return nil
 }

main.go

@@ -48,7 +48,13 @@ func main() {
 				Name:    "list",
 				Usage:   "List all available go versions",
 				Aliases: []string{"ls", "l"},
-				Action:  cmd.ListCommand,
+				Flags: []cli.Flag{
+					&cli.BoolFlag{
+						Name:    "available",
+						Aliases: []string{"a"},
+					},
+				},
+				Action: cmd.ListCommand,
 			},
 		},
 		HideHelpCommand: true,