Allow msgbus CLI to get config from cli options, env and config (12-factor)

cmd/msgbus/pub.go

@@ -6,6 +6,7 @@ import (
 	"os"
 
 	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
 
 	"github.com/prologic/msgbus/client"
 )
@@ -21,7 +22,7 @@ This is an asynchronous operation and does not wait for a response unless the
 -w/--wait option is also present.`,
 	Args: cobra.MinimumNArgs(1),
 	Run: func(cmd *cobra.Command, args []string) {
-		uri := cmd.Flag("uri").Value.String()
+		uri := viper.GetString("uri")
 		client := client.NewClient(uri, nil)
 
 		topic := args[0]

cmd/msgbus/pull.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
 
 	"github.com/prologic/msgbus/client"
 )
@@ -18,7 +19,7 @@ This is primarily useful in situations where a subscription was lost and you
 want to "catch up" and pull any messages left in the queue for that topic.`,
 	Args: cobra.MinimumNArgs(1),
 	Run: func(cmd *cobra.Command, args []string) {
-		uri := cmd.Flag("uri").Value.String()
+		uri := viper.GetString("uri")
 		client := client.NewClient(uri, nil)
 
 		topic := args[0]

cmd/msgbus/root.go

@@ -3,6 +3,7 @@ package main
 import (
 	"fmt"
 	"os"
+	"strings"
 
 	"github.com/mitchellh/go-homedir"
 	"github.com/spf13/cobra"
@@ -47,6 +48,9 @@ func init() {
 		"uri", "u", "http://localhost:8000",
 		"URI to connect to msgbusd",
 	)
+
+	viper.BindPFlag("uri", RootCmd.PersistentFlags().Lookup("uri"))
+	viper.SetDefault("uri", "http://localhost:8000/")
 }
 
 // initConfig reads in config file and ENV variables if set.
@@ -62,11 +66,13 @@ func initConfig() {
 			os.Exit(1)
 		}
 
-		// Search config in home directory with name ".cobra-example" (without extension).
 		viper.AddConfigPath(home)
-		viper.SetConfigName(".cobra-example")
+		viper.SetConfigName(".msgbus.yaml")
 	}
 
+	// from the environment
+	viper.SetEnvPrefix("MSGBUS")
+	viper.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))
 	viper.AutomaticEnv() // read in environment variables that match
 
 	// If a config file is found, read it in.

cmd/msgbus/sub.go

@@ -7,6 +7,7 @@ import (
 	"syscall"
 
 	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
 
 	"github.com/prologic/msgbus/client"
 )
@@ -19,7 +20,7 @@ var subCmd = &cobra.Command{
 to the topic, the message is printed to standard output.`,
 	Args: cobra.MinimumNArgs(1),
 	Run: func(cmd *cobra.Command, args []string) {
-		uri := cmd.Flag("uri").Value.String()
+		uri := viper.GetString("uri")
 		client := client.NewClient(uri, nil)
 
 		topic := args[0]