added real world example program

.gitignore

@@ -0,0 +1,2 @@
+
+example/example

example/main.go

@@ -0,0 +1,41 @@
+package main
+
+/*
+
+  In Terminal:
+
+    # build the file
+    go build -o example
+
+    # set the environment variable
+    TEST_STRING=Hello
+
+    # run the code
+    ./example
+
+    # run the code with a different variable for
+    # this particular execution of the program
+    TEST_STRING=Goodbye ./example
+
+*/
+
+import (
+	"log"
+
+	"github.com/joeshaw/envdecode"
+)
+
+type config struct {
+	TestString string `env:"TEST_STRING"`
+}
+
+func main() {
+
+	var cfg config
+	if err := envdecode.Decode(&cfg); err != nil {
+		log.Fatalf("Failed to decode: %s", err)
+	}
+
+	log.Println("TEST_STRING:", cfg.TestString)
+
+}