go-cache/README

go-cache is an in-memory key:value store/cache similar to memcached that is suitable for
applications running on a single machine. Any object can be stored, for a given duration
or forever, and the cache can be used safely by multiple goroutines.

Installation:
    goinstall github.com/pmylund/go-cache

Usage:
    // 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 "yes", with no expiration time (the item
    // won't be removed until it is re-set, or removed using c.Delete("baz")
    c.Set("baz", "yes", -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 cache does not serialize its data, 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:

func New(de, ci time.Duration) *Cache
    Returns a new cache with a given default expiration duration and default cleanup
    interval. If the expiration duration is less than 1, the items in the cache never
    expire and must be deleted manually. If the cleanup interval is less than one,
    expired items are not deleted from the cache before their next lookup or before
    calling DeleteExpired.

func (c *Cache) Set(k string, x interface{}, d time.Duration)
    Adds an item to the cache, replacing any existing item. If the duration is 0, the
    cache's default expiration time is used. If it is -1, the item never expires.

func (c *Cache) Add(k string, x interface{}, d time.Duration) error
    Adds an item to the cache only if an item doesn't already exist for the given key,
    or if the existing item has expired. Returns an error if not.

func (c *Cache) Replace(k string, x interface{}, d time.Duration) error
    Sets a new value for the cache item only if it already exists. Returns an error if
    it does not.

func (c *Cache) Get(k string) (interface{}, bool)
    Gets an item from the cache. Returns the item or nil, and a bool indicating whether
    the given key was found in the cache.

func (c *Cache) Increment(k string, n int64) error
    Increment an item of type int, int8, int16, int32, int64, uintptr, uint, uint8,
    uint32, or uint64, float32 or float64 by n. Returns an error if the item's value
    is not an integer, if it was not found, or if it is not possible to increment it
    by n. Passing a negative number will cause the item to be decremented.

func (c *Cache) IncrementFloat(k string, n float64) error
    Increment an item of type int, int8, int16, int32, int64, uintptr, uint, uint8,
    uint32, uint64, float32 or float64 by n. Returns an error if the item's value is
    not an integer, if it was not found, or if it is not possible to increment it by
    n. Passing a negative number will cause the item to be decremented.

func (c *Cache) Decrement(k string, n int64) error
    Decrement an item of type int, int8, int16, int32, int64, uintptr, uint, uint8,
    uint32, or uint64, float32 or float64 by n. Returns an error if the item's value
    is not an integer, if it was not found, or if it is not possible to decrement it
    by n.

func (c *Cache) Delete(k string)
    Deletes an item from the cache. Does nothing if the item does not exist in the cache.

func (c *Cache) DeleteExpired()
    Deletes all expired items from the cache.

func (c *Cache) Flush()
    Deletes all items from the cache.