Building and returning JWTs on login

* Created Util package for assorted items
* Currently generates an HMAC key on startup, to be changed
* JWT also includes login role

models/admin.go

@@ -2,8 +2,11 @@ package models
 
 import (
 	"errors"
+	"time"
 
+	"github.com/golang-jwt/jwt"
 	"github.com/yxzzy-wtf/gin-gonic-prepack/database"
+	"github.com/yxzzy-wtf/gin-gonic-prepack/util"
 )
 
 type Admin struct {
@@ -11,8 +14,26 @@ type Admin struct {
 	Email string
 }
 
+const adminJwtDuration = time.Hour * 2
+
+var adminHmac = util.GenerateHmac()
+
 func (a *Admin) GetJwt() (string, int) {
-	return "", 0
+	exp := time.Now().Add(adminJwtDuration)
+	j := jwt.NewWithClaims(jwt.SigningMethodHS256, jwt.MapClaims{
+		"sub":  a.Uid.String(),
+		"iat":  time.Now(),
+		"exp":  exp,
+		"role": "admin",
+	})
+
+	jstr, err := j.SignedString(adminHmac)
+	if err != nil {
+		// we should ALWAYS be able to build and sign a str
+		panic(err)
+	}
+
+	return jstr, int(adminJwtDuration.Seconds())
 }
 
 func (a *Admin) ByEmail(email string) error {