decoder

Note - The latest version supports only go 1.11 or later since swithcing to go modules. For older versions of go, pin to the v0.2.3 tag.

Package decoder - this unmarshals or decodes values from a consul KV store into a struct. The following types are supported:

• integer (int/int8/int16/int32/int64)

• unsigned (uint/uint8/uint16/uint32/uint64)

• float (float64/float32)

• bool

• time.Duration

• net.IP

• net.IPMask

• struct - nested struct by default implies a consul folder with the same name. if the tag modifier "json" is encountered, then the value of in the KV is unmarshaled as json using json.Unmarshal

• slice - the type can be most of the supported types, except another slice.

• map - the key must be a string, the value can be anything but another map.

• encoding.TextUnmarshaler - any type that implements this will have its UnmarshalText() method called.

Struct tags

By default, the decoder packages looks for the struct tag "decoder". However, this can be overridden inside the Decoder struct as shown below. For the purposes of examples, we'll stick with the default "decoder" tag. By default, in the absence of a decoder tag, it will look for a consul key name with the same name as the struct field. Only exported struct fields are considered. The name comparison is case-insensitive by default, but this is configurable in the Decoder struct. the tag "-" indicates to skip the field. The modifier ",json" appended to the end signals that the value is to be interpreted as json and unmarshaled rather than interpreted. Similarly, the modififier ",csv" allows comma separated values to be read into a slice, and ",ssv" allows space separated values to be read intoa slice. For csv and ssv, slices of string, numeric and boolean are supported.

    struct Foo {

        // populate the value from key "whatever" into FooField1
        FooField1 string `decoder:"whatever"`

        // skip populating FooField2, "-" signals skip
        FooField2 string `decoder:"-"`

        // this looks for a folder named FooField3
        // and maps keys inside to the keys / values of the map.  string
        // is the only valid key type, though the map value can be most any
        // of the other types supported by this package.  Notable exception
        // map, as nested maps are not allowed.  You can, however, have a
        // map[string]SomeStruct.
        FooField3 map[string]string

        // this looks for a folder named FooField4 (case insensitive)
        // this is similar to the map example above, but it ignores the keys
        // inside and maps the values in-order into the slice.  nested slices
        // are not allowed, i.e., [][]string.
        FooField4 []string

        // this interprets the value of foofield5 as json data and
        // will send it to json.Unmarshal from encoding/json package.
        FooField5 *SomeStruct `decoder:"foofield5,json"`

        // this expects there to be a consul folder foofield6 and that the
        // keys within will correspond to the fields inside SomeStruct type.
        FooField6 *SomeStruct `decoder:"foofield6"`

        // It is possible to specify arbitrarily nested values by giving
        // the path in the struct tag.
        FooField7 string `decoder:"arbitrarily/nested/key"`

        // Comma separated values are supported.  This uses the encoding/csv
        // package, so all variations supported by it are supported here.
        FooField8 []string `decoder:",csv"`

        // Space separated values are supported.  This uses strings.Fields
        // for parsing, so see that documentation for information.
        FooField9 []string `decoder:",ssv"`
}