Sling is a Go HTTP client library for creating and sending API requests.
Slings store HTTP Request properties to simplify sending requests and decoding responses. Check usage or the examples to learn how to compose a Sling into your API client.
- Method Setters: Get/Post/Put/Patch/Delete/Head
- Add or Set Request Headers
- Base/Path: Extend a Sling for different endpoints
- Encode structs into URL query parameters
- Encode a form or JSON into the Request Body
- Receive JSON success or failure responses
go get github.com/dghubble/sling
Read GoDoc
Use a Sling to set path, method, header, query, or body properties and create an http.Request
.
type Params struct {
Count int `url:"count,omitempty"`
}
params := &Params{Count: 5}
req, err := sling.New().Get("https://example.com").QueryStruct(params).Request()
client.Do(req)
Use Path
to set or extend the URL for created Requests. Extension means the path will be resolved relative to the existing URL.
// creates a GET request to https://example.com/foo/bar
req, err := sling.New().Base("https://example.com/").Path("foo/").Path("bar").Request()
Use Get
, Post
, Put
, Patch
, Delete
, or Head
which are exactly the same as Path
except they set the HTTP method too.
req, err := sling.New().Post("http://upload.com/gophers")
Add
or Set
headers for requests created by a Sling.
s := sling.New().Base(baseUrl).Set("User-Agent", "Gophergram API Client")
req, err := s.New().Get("gophergram/list").Request()
Define url tagged structs. Use QueryStruct
to encode a struct as query parameters on requests.
// Github Issue Parameters
type IssueParams struct {
Filter string `url:"filter,omitempty"`
State string `url:"state,omitempty"`
Labels string `url:"labels,omitempty"`
Sort string `url:"sort,omitempty"`
Direction string `url:"direction,omitempty"`
Since string `url:"since,omitempty"`
}
githubBase := sling.New().Base("https://api.github.com/").Client(httpClient)
path := fmt.Sprintf("repos/%s/%s/issues", owner, repo)
params := &IssueParams{Sort: "updated", State: "open"}
req, err := githubBase.New().Get(path).QueryStruct(params).Request()
Define JSON tagged structs. Use BodyJSON
to JSON encode a struct as the Body on requests.
type IssueRequest struct {
Title string `json:"title,omitempty"`
Body string `json:"body,omitempty"`
Assignee string `json:"assignee,omitempty"`
Milestone int `json:"milestone,omitempty"`
Labels []string `json:"labels,omitempty"`
}
githubBase := sling.New().Base("https://api.github.com/").Client(httpClient)
path := fmt.Sprintf("repos/%s/%s/issues", owner, repo)
body := &IssueRequest{
Title: "Test title",
Body: "Some issue",
}
req, err := githubBase.New().Post(path).BodyJSON(body).Request()
Requests will include an application/json
Content-Type header.
Define url tagged structs. Use BodyForm
to form url encode a struct as the Body on requests.
type StatusUpdateParams struct {
Status string `url:"status,omitempty"`
InReplyToStatusId int64 `url:"in_reply_to_status_id,omitempty"`
MediaIds []int64 `url:"media_ids,omitempty,comma"`
}
tweetParams := &StatusUpdateParams{Status: "writing some Go"}
req, err := twitterBase.New().Post(path).BodyForm(tweetParams).Request()
Requests will include an application/x-www-form-urlencoded
Content-Type header.
Use Body
to set a plain io.Reader
on requests created by a Sling.
body := strings.NewReader("raw body")
req, err := sling.New().Base("https://example.com").Body(body).Request()
Set a content type header, if desired (e.g. Set("Content-Type", "text/plain")
).
Each Sling creates a standard http.Request
(e.g. with some path and query
params) each time Request()
is called. You may wish to extend an existing Sling to minimize duplication (e.g. a common client or base url).
Each Sling instance provides a New()
method which creates an independent copy, so setting properties on the child won't mutate the parent Sling.
const twitterApi = "https://api.twitter.com/1.1/"
base := sling.New().Base(twitterApi).Client(authClient)
// statuses/show.json Sling
tweetShowSling := base.New().Get("statuses/show.json").QueryStruct(params)
req, err := tweetShowSling.Request()
// statuses/update.json Sling
tweetPostSling := base.New().Post("statuses/update.json").BodyForm(params)
req, err := tweetPostSling.Request()
Without the calls to base.New()
, tweetShowSling
and tweetPostSling
would reference the base Sling and POST to
"https://api.twitter.com/1.1/statuses/show.json/statuses/update.json", which
is undesired.
Recap: If you wish to extend a Sling, create a new child copy with New()
.
Define a JSON struct to decode a type from 2XX success responses. Use ReceiveSuccess(successV interface{})
to send a new Request and decode the response body into successV
if it succeeds.
// Github Issue (abbreviated)
type Issue struct {
Title string `json:"title"`
Body string `json:"body"`
}
issues := new([]Issue)
resp, err := githubBase.New().Get(path).QueryStruct(params).ReceiveSuccess(issues)
fmt.Println(issues, resp, err)
Most APIs return failure responses with JSON error details. To decode these, define success and failure JSON structs. Use Receive(successV, failureV interface{})
to send a new Request that will automatically decode the response into the successV
for 2XX responses or into failureV
for non-2XX responses.
type GithubError struct {
Message string `json:"message"`
Errors []struct {
Resource string `json:"resource"`
Field string `json:"field"`
Code string `json:"code"`
} `json:"errors"`
DocumentationURL string `json:"documentation_url"`
}
issues := new([]Issue)
githubError := new(GithubError)
resp, err := githubBase.New().Get(path).QueryStruct(params).Receive(issues, githubError)
fmt.Println(issues, githubError, resp, err)
Pass a nil successV
or failureV
argument to skip JSON decoding into that value.
APIs typically define an endpoint (also called a service) for each type of resource. For example, here is a tiny Github IssueService which lists repository issues.
const baseURL = "https://api.github.com/"
type IssueService struct {
sling *sling.Sling
}
func NewIssueService(httpClient *http.Client) *IssueService {
return &IssueService{
sling: sling.New().Client(httpClient).Base(baseURL),
}
}
func (s *IssueService) ListByRepo(owner, repo string, params *IssueListParams) ([]Issue, *http.Response, error) {
issues := new([]Issue)
githubError := new(GithubError)
path := fmt.Sprintf("repos/%s/%s/issues", owner, repo)
resp, err := s.sling.New().Get(path).QueryStruct(params).Receive(issues, githubError)
if err == nil {
err = githubError
}
return *issues, resp, err
}
- Digits dghubble/go-digits
- GoSquared drinkin/go-gosquared
- Kala ajvb/kala
- Parse fergstar/go-parse
- Rdio apriendeau/shares
- Swagger Generator swagger-api/swagger-codegen
- Twitter dghubble/go-twitter
- Hacker News mirceamironenco/go-hackernews
- Stacksmith jesustinoco/go-smith
Create a Pull Request to add a link to your own API.
Many client libraries follow the lead of google/go-github (our inspiration!), but do so by reimplementing logic common to all clients.
This project borrows and abstracts those ideas into a Sling, an agnostic component any API client can use for creating and sending requests.
See the Contributing Guide.