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context.go
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context.go
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package context
import (
"context"
"time"
)
// Context wrapper
type Context struct {
ctx context.Context
cancel context.CancelFunc
}
func TODO() context.Context {
return context.TODO()
}
func Background() context.Context {
return context.Background()
}
// NewContext return a context. Timeout is in seconds, zero means no timeout
func NewContext(timeout time.Duration) *Context {
var ctx context.Context
var cancel context.CancelFunc
if timeout == 0 {
ctx, cancel = context.WithCancel(context.Background())
} else {
ctx, cancel = context.WithTimeout(context.Background(), timeout*time.Second)
}
return &Context{
ctx: ctx,
cancel: cancel,
}
}
// Deadline returns the time when work done on behalf of this context
// should be canceled. Deadline returns ok==false when no deadline is
// set. Successive calls to Deadline return the same results.
func (c *Context) Deadline() (deadline time.Time, ok bool) {
return c.ctx.Deadline()
}
// Done returns a channel that's closed when work done on behalf of this
// context should be canceled. Done may return nil if this context can
// never be canceled. Successive calls to Done return the same value.
//
// WithCancel arranges for Done to be closed when cancel is called;
// WithDeadline arranges for Done to be closed when the deadline
// expires; WithTimeout arranges for Done to be closed when the timeout
// elapses.
//
// Done is provided for use in select statements:
//
// // Stream generates values with DoSomething and sends them to out
// // until DoSomething returns an error or ctx.Done is closed.
// func Stream(ctx context.Context, out chan<- Value) error {
// for {
// v, err := DoSomething(ctx)
// if err != nil {
// return err
// }
// select {
// case <-ctx.Done():
// return ctx.Err()
// case out <- v:
// }
// }
// }
//
// See https://blog.golang.org/pipelines for more examples of how to use
// a Done channel for cancelation.
func (c *Context) Done() <-chan struct{} {
return c.ctx.Done()
}
// Err as string
// If Done is not yet closed, Err returns nil.
// If Done is closed, Err returns a non-nil error explaining why:
// Canceled if the context was canceled
// or DeadlineExceeded if the context's deadline passed.
// After Err returns a non-nil error, successive calls to Err return the same error.
func (c *Context) Err() error {
return c.ctx.Err()
}
// Value returns the value associated with this context for key, or nil
// if no value is associated with key. Successive calls to Value with
// the same key returns the same result.
//
// Use context values only for request-scoped data that transits
// processes and API boundaries, not for passing optional parameters to
// functions.
//
// A key identifies a specific value in a Context. Functions that wish
// to store values in Context typically allocate a key in a global
// variable then use that key as the argument to context.WithValue and
// Context.Value. A key can be any type that supports equality;
// packages should define keys as an unexported type to avoid
// collisions.
//
// Packages that define a Context key should provide type-safe accessors
// for the values stored using that key:
//
// // Package user defines a User type that's stored in Contexts.
// package user
//
// import "context"
//
// // User is the type of value stored in the Contexts.
// type User struct {...}
//
// // key is an unexported type for keys defined in this package.
// // This prevents collisions with keys defined in other packages.
// type key int
//
// // userKey is the key for user.User values in Contexts. It is
// // unexported; clients use user.NewContext and user.FromContext
// // instead of using this key directly.
// var userKey key
//
// // NewContext returns a new Context that carries value u.
// func NewContext(ctx context.Context, u *User) context.Context {
// return context.WithValue(ctx, userKey, u)
// }
//
// // FromContext returns the User value stored in ctx, if any.
// func FromContext(ctx context.Context) (*User, bool) {
// u, ok := ctx.Value(userKey).(*User)
// return u, ok
// }
func (c *Context) Value(key interface{}) interface{} {
return c.ctx.Value(key)
}
// Cancel the current context
func (c *Context) Cancel() {
c.cancel()
}
// WithValue returns a copy of parent in which the value associated with key is
// val.
//
// Use context Values only for request-scoped data that transits processes and
// APIs, not for passing optional parameters to functions.
//
// The provided key must be comparable and should not be of type
// string or any other built-in type to avoid collisions between
// packages using context. Users of WithValue should define their own
// types for keys. To avoid allocating when assigning to an
// interface{}, context keys often have concrete type
// struct{}. Alternatively, exported context key variables' static
// type should be a pointer or interface.
func (c *Context) WithValue(key, val interface{}) {
c.ctx = context.WithValue(c.ctx, key, val)
}
// Context returns the embed context object
func (c *Context) Context() context.Context {
return c.ctx
}