cache

go-cache is an in-memory key:value store/cache similar to memcached that is
suitable for applications running on a single machine. Its major advantage is
that, being essentially a thread-safe map[string]interface{} with expiration
times, it doesn't need to serialize or transmit its contents over the network.

Any object can be stored, for a given duration or forever, and the cache can be
safely used by multiple goroutines.

Although go-cache isn't meant to be used as a persistent datastore, the entire
cache may be saved to and loaded from a file (or any io.Reader/Writer) to
recover from downtime quickly.

== Installation

go get github.com/pmylund/go-cache

== Usage

import "github.com/pmylund/go-cache"

// Create a cache with a default expiration time of 5 minutes, and which
// purges expired items every 30 seconds
c := cache.New(5*time.Minute, 30*time.Second)

// Set the value of the key "foo" to "bar", with the default expiration time
c.Set("foo", "bar", 0)

// Set the value of the key "baz" to 42, with no expiration time
// (the item won't be removed until it is re-set, or removed using
// c.Delete("baz")
c.Set("baz", 42, -1)

// Get the string associated with the key "foo" from the cache
foo, found := c.Get("foo")
if found {
        fmt.Println(foo)
}

// Since Go is statically typed, and cache values can be anything, type
// assertion is needed when values are being passed to functions that don't
// take arbitrary types, (i.e. interface{}). The simplest way to do this for
// values which will only be used once--e.g. for passing to another
// function--is:
foo, found := c.Get("foo")
if found {
        MyFunction(foo.(string))
}

// This gets tedious if the value is used several times in the same function.
// You might do either of the following instead:
if x, found := c.Get("foo"); found {
        foo := x.(string)
        ...
}
// or
var foo string
if x, found := c.Get("foo"); found {
        foo = x.(string)
}
...
// foo can then be passed around freely as a string

// Want performance? Store pointers!
c.Set("foo", &MyStruct, 0)
if x, found := c.Get("foo"); found {
        foo := x.(*MyStruct)
        ...
}

// If you store a reference type like a pointer, slice, map or channel, you
// do not need to run Set if you modify the underlying data. The cached
// reference points to the same memory, so if you modify a struct whose
// pointer you've stored in the cache, retrieving that pointer with Get will
// point you to the same data:
foo := &MyStruct{Num: 1}
c.Set("foo", foo, 0)
...
x, _ := c.Get("foo")
foo := x.(*MyStruct)
fmt.Println(foo.Num)
...
foo.Num++
...
x, _ := c.Get("foo")
foo := x.(*MyStruct)
foo.Println(foo.Num)

// will print:
1
2

== Reference

`go doc` or http://godoc.org/github.com/pmylund/go-cache