* support bind http header param #1956
update #1956
```
package main
import (
"fmt"
"github.com/gin-gonic/gin"
)
type testHeader struct {
Rate int `header:"Rate"`
Domain string `header:"Domain"`
}
func main() {
r := gin.Default()
r.GET("/", func(c *gin.Context) {
h := testHeader{}
if err := c.ShouldBindHeader(&h); err != nil {
c.JSON(200, err)
}
fmt.Printf("%#v\n", h)
c.JSON(200, gin.H{"Rate": h.Rate, "Domain": h.Domain})
})
r.Run()
// client
// curl -H "rate:300" -H "domain:music" 127.0.0.1:8080/
// output
// {"Domain":"music","Rate":300}
}
```
* add unit test
* Modify the code to get the http header
When the http header is obtained in the standard library,
the key value will be modified by the CanonicalMIMEHeaderKey function,
and finally the value of the http header will be obtained from the map.
As follows.
```go
func (h MIMEHeader) Get(key string) string {
// ...
v := h[CanonicalMIMEHeaderKey(key)]
// ...
}
```
This pr also follows this modification
* Thanks to vkd for suggestions, modifying code
* Increase test coverage
env GOPATH=`pwd` go test github.com/gin-gonic/gin/binding -coverprofile=cover.prof
ok github.com/gin-gonic/gin/binding 0.015s coverage: 100.0% of statements
* Rollback check code
* add use case to README.md
* move tests of mapping to separate test file
make 100% coverage of form_mapping.go from form_mapping_test.go file
* fix tests for go 1.6
go 1.6 doesn't support `t.Run(...)` subtests
* refactor(form_mapping.go): mapping ptr, struct and map
* fix#1672 correct work with ptr - not create value if field is not set
* avoid allocations on strings.Split() - change to strings.Index()
* fix#610 tag value "-" is mean ignoring field
* struct fields mapped like json.Unmarshal
* map fields mapped like json.Unmarshal
* fix after @thinkerou review
* support bind uri (1)
* uri binding successful run
* fix vet warning: github.com/gin-gonic/gin/internal.Param composite literal uses unkeyed fields
* fix code style
* update function name
* fix test function signature
* add test for CanSet
* update readme and add test case
* remove internal.Params
* add coverage
* fix warning
* support default value for form
* fix bug for nil interface
* use SplitN and optimization code
* add test case
* add test cases for form(own default value)
* fix invalid code
* fix code indent
* assert order
