Copyright 2019, OpenCensus Authors Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

package tag
valueTTLNoPropagation prevents tag from propagating.
	valueTTLNoPropagation = 0
valueTTLUnlimitedPropagation allows tag to propagate without any limits on number of hops.
	valueTTLUnlimitedPropagation = -1
)
TTL is metadata that specifies number of hops a tag can propagate. Details about TTL metadata is specified at https://github.com/census-instrumentation/opencensus-specs/blob/master/tags/TagMap.md#tagmetadata
type TTL struct {
	ttl int
}
TTLUnlimitedPropagation is TTL metadata that allows tag to propagate without any limits on number of hops.
	TTLUnlimitedPropagation = TTL{ttl: valueTTLUnlimitedPropagation}
TTLNoPropagation is TTL metadata that prevents tag from propagating.
	TTLNoPropagation = TTL{ttl: valueTTLNoPropagation}
)

type metadatas struct {
	ttl TTL
}
Metadata applies metadatas specified by the function.
type Metadata func(*metadatas)
WithTTL applies metadata with provided ttl.
func ( TTL) Metadata {
	return func( *metadatas) {
		.ttl = 
	}