substitution cipher implementation

Reads in a json file that has a map of letters to letters

psyfer/substitution.go

@@ -1,4 +1,36 @@
 package psyfer
 
-func ReadConfig() {
+import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"log"
+)
+
+type KeyJSON struct {
+	Key map[string]string `json:"key"`
+}
+
+var k = KeyJSON{}
+
+func ReadConfig() {
+	dat, err := ioutil.ReadFile("key.json")
+	if err != nil {
+		log.Fatal(err)
+	}
+	json.Unmarshal([]byte(dat), &k)
+	fmt.Println(k.Key["a"])
+}
+
+func Substitution(input string) string {
+	inputSlice := []string{}
+	output := ""
+	for _, char := range input {
+		inputSlice = append(inputSlice, string(char))
+	}
+	for i := range inputSlice {
+		output += k.Key[inputSlice[i]]
+	}
+	fmt.Println(output)
+	return output
 }