chain

Documentation

Index

• type Chain
  • func New(middlewares ...Middleware) Chain
  • func (c Chain) Append(middlewares ...Middleware) Chain
  • func (c Chain) Then(h http.Handler) http.Handler
  • func (c Chain) ThenFunc(fn http.HandlerFunc) http.Handler
• type Middleware

Types

type Chain

type Chain []Middleware

Chain acts as a list of http.Handler middlewares. Chain is effectively immutable: once created, it will always hold the same set of middlewares in the same order.

func New

func New(middlewares ...Middleware) Chain

New creates a new chain, memorizing the given list of middlewares. New serves no other function, middlewares are only constructed upon a call to Then().

func (Chain) Append

func (c Chain) Append(middlewares ...Middleware) Chain

Append extends a chain, adding the specified middlewares as the last ones in the request flow.

chain := chain.New(m1, m2)
chain = chain.Append(m3, m4)
// requests in chain go m1 -> m2 -> m3 -> m4

func (Chain) Then

func (c Chain) Then(h http.Handler) http.Handler

Then chains the middleware and returns the final http.Handler.

chain.New(m1, m2, m3).Then(h)

is equivalent to:

m1(m2(m3(h)))

When the request comes in, it will be passed to m1, then m2, then m3 and finally, the given handler (assuming every middleware calls the following one).

A chain can be safely reused by calling Then() several times.

chain := chain.New(ratelimitHandler, csrfHandler)
indexPipe = chain.Then(indexHandler)
authPipe  = chain.Then(authHandler)

Note that middlewares are called on every call to Then() and thus several instances of the same middleware will be created when a chain is reused in this previous example. For proper middleware, this should cause no problems.

Then() treats nil as http.DefaultServeMux.

func (Chain) ThenFunc

func (c Chain) ThenFunc(fn http.HandlerFunc) http.Handler

ThenFunc works identically to Then, but takes a HandlerFunc instead of a Handler.

The following two statements are equivalent:

c.Then(http.HandlerFunc(fn))
c.ThenFunc(fn)

ThenFunc provides all the guarantees of Then.

type Middleware

type Middleware func(http.Handler) http.Handler

Middleware is a constructor function returning a http.Handler.