invalid character 'F' looking for beginning of object key stringというエラーが出ます。

curl http://localhost:8080/users/ -X POST -H "Content-Type: application/json" -d '{"FirstName": "Rikka", "LastName": "Takarada"}'をしているのですがデータベースに保存されずinvalid character 'F' looking for beginning of object key stringというものが出ます。これはどのように解決すればいいでしょうか？

user_controller.go
1package user
2
3import (
4	"fmt"
5
6	"github.com/gin-gonic/gin"
7
8	user "background/service"
9)
10
11type Controller struct{}
12
13// 検索 GET /books
14func (pc Controller) Index(c *gin.Context) {
15	// パラメータ取得
16	var s user.Service
17	p, err := s.GetAll()
18
19	if err != nil {
20		c.AbortWithStatus(404)
21		fmt.Println(err)
22	} else {
23		c.JSON(200, p)
24	}
25}
26func (pc Controller) Create(c *gin.Context) {
27	var s user.Service
28	p, err := s.CreateModel(c)
29
30	if err != nil {
31		c.AbortWithStatus(400)
32		fmt.Println(err)
33	} else {
34		c.JSON(201, p)
35	}
36}
37
38// Show action: GET /users/:id
39func (pc Controller) Show(c *gin.Context) {
40	id := c.Params.ByName("id")
41	var s user.Service
42	p, err := s.GetByID(id)
43
44	if err != nil {
45		c.AbortWithStatus(404)
46		fmt.Println(err)
47	} else {
48		c.JSON(200, p)
49	}
50}
51
52// Update action: PUT /users/:id
53func (pc Controller) Update(c *gin.Context) {
54	id := c.Params.ByName("id")
55	var s user.Service
56	p, err := s.UpdateByID(id, c)
57
58	if err != nil {
59		c.AbortWithStatus(400)
60		fmt.Println(err)
61	} else {
62		c.JSON(200, p)
63	}
64}
65
66// Delete action: DELETE /users/:id
67func (pc Controller) Delete(c *gin.Context) {
68	id := c.Params.ByName("id")
69	var s user.Service
70
71	if err := s.DeleteByID(id); err != nil {
72		c.AbortWithStatus(403)
73		fmt.Println(err)
74	} else {
75		c.JSON(204, gin.H{"id #" + id: "deleted"})
76	}
77}

user_server.go
1package server
2
3import (
4	"github.com/gin-gonic/gin"
5
6	user "background/controller"
7)
8
9// 初期化
10func Init() {
11	r := router()
12
13	r.Run()
14}
15
16// ルーティング
17func router() *gin.Engine {
18	r := gin.Default()
19
20	u := r.Group("/users")
21	{
22		ctrl := user.Controller{}
23		u.GET("", ctrl.Index)
24		u.GET("/:id", ctrl.Show)
25		u.POST("", ctrl.Create)
26		u.PUT("/:id", ctrl.Update)
27		u.DELETE("/:id", ctrl.Delete)
28	}
29
30	return r
31}

package entity

// User is user models property
type User struct {
	ID        uint   `json:"id"`
	FirstName string `json:"firstname"`
	LastName  string `json:"lastname"`
}

user_service.go
1package user
2
3import (
4	"background/db"
5	"background/entity"
6
7	"github.com/gin-gonic/gin"
8)
9
10type Service struct{}
11
12type User entity.User
13
14func (s Service) GetAll() ([]User, error) {
15	db := db.GetDB()
16	var u []User
17
18	if err := db.Find(&u).Error; err != nil {
19		return nil, err
20	}
21
22	return u, nil
23}
24
25// CreateModel is create User model
26func (s Service) CreateModel(c *gin.Context) (User, error) {
27	db := db.GetDB()
28	var u User
29
30	if err := c.BindJSON(&u); err != nil {
31		return u, err
32	}
33
34	if err := db.Create(&u).Error; err != nil {
35		return u, err
36	}
37
38	return u, nil
39}
40
41// GetByID is get a User
42func (s Service) GetByID(id string) (User, error) {
43	db := db.GetDB()
44	var u User
45
46	if err := db.Where("id = ?", id).First(&u).Error; err != nil {
47		return u, err
48	}
49
50	return u, nil
51}
52
53// UpdateByID is update a User
54func (s Service) UpdateByID(id string, c *gin.Context) (User, error) {
55	db := db.GetDB()
56	var u User
57
58	if err := db.Where("id = ?", id).First(&u).Error; err != nil {
59		return u, err
60	}
61
62	if err := c.BindJSON(&u); err != nil {
63		return u, err
64	}
65
66	db.Save(&u)
67
68	return u, nil
69}
70
71// DeleteByID is delete a User
72func (s Service) DeleteByID(id string) error {
73	db := db.GetDB()
74	var u User
75
76	if err := db.Where("id = ?", id).Delete(&u).Error; err != nil {
77		return err
78	}
79
80	return nil
81}
82