golang gin web framework, invalid memory address or nil pointer dereference

I'm doing tests with gin and gorm , I have the following program:

package main

import (
    "fmt"
    "github.com/gin-gonic/gin"
    "github.com/jinzhu/gorm"
    _ "github.com/jinzhu/gorm/dialects/mysql"
)

var db *gorm.DB
var err error

type Person struct {
    ID uint 'gorm:"primary_key"'
    FirstName string
    LastName string
}

func main() {
    // NOTE: See we’re using = to assign the global var
    // instead of := which would assign it only in this function
    db, err := gorm.Open("mysql", "santo:asdf@/test?charset=utf8&parseTime=True&loc=Local")

    if err != nil {
        fmt.Println(err)
    }
    defer db.Close()
    db.AutoMigrate(&Person{})

    r := gin.Default()
    r.GET("/people/", GetPeople)
    r.GET("/people/:id", GetPerson)
    r.POST("/people", CreatePerson)
    r.PUT("/people/:id", UpdatePerson)
    r.DELETE("/people/:id", DeletePerson)
    r.Run(":8080")
}

func DeletePerson(c *gin.Context) {
    id := c.Params.ByName("id")
    var person Person
    d := db.Where("id = ?", id).Delete(&person)
    fmt.Println(d)
    c.JSON(200, gin.H{"id #" + id: "deleted"})
}

func UpdatePerson(c *gin.Context) {
    var person Person
    id := c.Params.ByName("id")
    if err := db.Where("id = ?", id).First(&person).Error; err != nil {
        c.AbortWithStatus(404)
        fmt.Println(err)
    }
    c.BindJSON(&person)
    db.Save(&person)
    c.JSON(200, person)
}

func CreatePerson(c *gin.Context) {
    var person Person
    c.BindJSON(&person)
    db.Create(&person)
    c.JSON(200, person)
}

func GetPerson(c *gin.Context) {
    id := c.Params.ByName("id")
    var person Person
    if err := db.Where("id = ?", id).First(&person).Error; err != nil {
        c.AbortWithStatus(404)
        fmt.Println(err)
    } else {
        c.JSON(200, person)
    }
}

func GetPeople(c *gin.Context) {
    var people []Person
    if err := db.Find(&people).Error; err != nil {
        c.AbortWithStatus(404)
        fmt.Println(err)
    } else {
        c.JSON(200, people)
    }
}

The program compiles well, the problem is at the moment of execution, when I make the call to the rest service:

http://localhost:8080/people/

I should show an empty array: []

But instead it shows me the following error in the console:

runtime error: invalid memory address or nil pointer dereference                                                          
/usr/local/go/src/runtime/panic.go:502 (0x42ab48)                                                                         

/usr/local/go/src/runtime/panic.go:63 (0x429bbd)                                                                          

/usr/local/go/src/runtime/signal_unix.go:388 (0x43f8f9)                                                                   

/home/santo/go/src/github.com/jinzhu/gorm/main.go:743 (0x8dab67)                                                          

/home/santo/go/src/github.com/jinzhu/gorm/main.go:168 (0x8d642e)                                                          

/home/santo/go/src/github.com/jinzhu/gorm/main.go:311 (0x8d7432)
        (*DB).Find: return s.NewScope(out).inlineCondition(where...).callCallbacks(s.parent.callbacks.queries).db
/home/santo/go/src/github.com/hectorgool/orm/main.go:79 (0x91a5bf)
        GetPeople: if err := db.Find(&people).Error; err != nil {
/home/santo/go/src/github.com/gin-gonic/gin/context.go:107 (0x88e252)
        (*Context).Next: c.handlers[c.index](c)
/home/santo/go/src/github.com/gin-gonic/gin/recovery.go:47 (0x89e639)
        RecoveryWithWriter.func1: c.Next()
/home/santo/go/src/github.com/gin-gonic/gin/context.go:107 (0x88e252)
        (*Context).Next: c.handlers[c.index](c)
/home/santo/go/src/github.com/gin-gonic/gin/logger.go:83 (0x89d8eb)
        LoggerWithWriter.func1: c.Next()
/home/santo/go/src/github.com/gin-gonic/gin/context.go:107 (0x88e252)
        (*Context).Next: c.handlers[c.index](c)
/home/santo/go/src/github.com/gin-gonic/gin/gin.go:359 (0x8959d5)
        (*Engine).handleHTTPRequest: c.Next()
/home/santo/go/src/github.com/gin-gonic/gin/gin.go:326 (0x895222)
        (*Engine).ServeHTTP: engine.handleHTTPRequest(c)
/usr/local/go/src/net/http/server.go:2694 (0x66520b)
        serverHandler.ServeHTTP: handler.ServeHTTP(rw, req)
/usr/local/go/src/net/http/server.go:1830 (0x6613c0)
        (*conn).serve: serverHandler{c.server}.ServeHTTP(w, w.req)
/usr/local/go/src/runtime/asm_amd64.s:2361 (0x456d20)
        goexit: BYTE    $0x90   // NOP

Someone can tell me what I'm doing wrong or what I'm missing