add config module

+package helper
+
+import (
+	"json"
+	"io/ioutil"
+	"log"
+)
+
+var config map[string]string
+
+func ReadConfig(filename string) {
+	contents, err := ioutil.ReadFile(filename)
+	if err != nil {
+		log.Exitf("Impossible to read %s", filename, err)
+	}
+	data, err := json.Decode(string(contents))
+	if err != nil {
+		log.Exitf("Can't parse %s as JSON", filename, err)
+	}
+	config = map[string]string{ }
+	for key, value := range data.(map[string]interface{ }) {
+		config[key] = value.(string)
+	}
+}
+
+func GetConfig(key string) string {
+	return config[key];
+}
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