Added key_reader to string_utils

string_utils/key_reader.go

+package string_utils
+
+import (
+	"os"
+	"strings"
+)
+
+//KeyReader is an interface to read string "<key>":"<value>" pairs
+//which is common to read from the environment
+//it is abstracted so the same interface can be implemented for
+//reading for example from REDIS and other sources
+type KeyReader interface {
+	Keys(prefix string) []string
+	GetString(key string) (value string, ok bool)
+}
+
+func EnvironmentKeyReader() KeyReader {
+	return envKeyReader{}
+}
+
+type envKeyReader struct{}
+
+func (envKeyReader) GetString(key string) (value string, ok bool) {
+	value = os.Getenv(key)
+	if value == "" {
+		return "", false
+	}
+	return value, true
+}
+
+func (envKeyReader) Keys(prefix string) []string {
+	keys := []string{}
+	for _, env := range os.Environ() {
+		if strings.HasPrefix(env, prefix) {
+			keys = append(keys, strings.SplitN(env, "=", 2)[0])
+		}
+	}
+	return keys
+}