add config

config/reader/preprocessor.go

@@ -0,0 +1,23 @@
+package reader
+
+import (
+	"os"
+	"regexp"
+)
+
+func ReplaceEnvVars(raw []byte) ([]byte, error) {
+	re := regexp.MustCompile(`\$\{([A-Za-z0-9_]+)\}`)
+	if re.Match(raw) {
+		dataS := string(raw)
+		res := re.ReplaceAllStringFunc(dataS, replaceEnvVars)
+		return []byte(res), nil
+	} else {
+		return raw, nil
+	}
+}
+
+func replaceEnvVars(element string) string {
+	v := element[2 : len(element)-1]
+	el := os.Getenv(v)
+	return el
+}