Use godotenv to load .env for development

.env.example

@@ -0,0 +1,5 @@
+TRANSMISSION_ADDR=http://localhost:9091
+TRANSMISSION_PASSWORD=
+TRANSMISSION_USERNAME=
+WEB_ADDR=:19091
+WEB_PATH=/metrics

.gitignore

@@ -1,3 +1,4 @@
+/.env
 /transmission-exporter
 
 *.o

README.md

@@ -19,12 +19,6 @@ ENV Variable | Description
 | TRANSMISSION_USERNAME | Transmission username, no default |
 | TRANSMISSION_PASSWORD | Transmission password, no default |
 
-### Build
-
-    make
-
-For development we encourage you to use `make install` instead, it's faster. 
-
 ### Docker
 
     docker pull metalmatze/transmission-exporter
@@ -49,6 +43,14 @@ Example `docker-compose.yml` with Transmission also running in docker.
       environment:
         TRANSMISSION_ADDR: http://transmission:9091
 
+### Development
+
+    make
+
+For development we encourage you to use `make install` instead, it's faster.
+
+Now simply copy the `.env.example` to `.env`, like `cp .env.example .env` and set your preferences.
+Now you're good to go.
 
 ### Original authors of the Transmission package  
 Tobias Blom (https://github.com/tubbebubbe/transmission)  

cmd/transmission-exporter/main.go

@@ -5,6 +5,7 @@ import (
 	"net/http"
 
 	arg "github.com/alexflint/go-arg"
+	"github.com/joho/godotenv"
 	transmission "github.com/metalmatze/transmission-exporter"
 	"github.com/prometheus/client_golang/prometheus"
 )
@@ -21,6 +22,11 @@ type Config struct {
 func main() {
 	log.Println("starting transmission-exporter")
 
+	err := godotenv.Load()
+	if err != nil {
+		log.Println("no .env present")
+	}
+
 	c := Config{
 		WebPath:          "/metrics",
 		WebAddr:          ":19091",