use of unstable library feature 'map_get_key_value'

[isnlan]

how to use in lib and unit test

error[E0658]: use of unstable library feature 'map_get_key_value'
--> /Users/snlan/.cargo/registry/src/proxy-git.cwkhome.fun-1ecc6299db9ec823/dashmap-3.7.0/src/lib.rs:609:37
|
609 | if let Some((k, v)) = shard.get_key_value(key) {
| ^^^^^^^^^^^^^
|
= note: for more information, see rust-lang/rust#49347

rustc 1.39.0 (4560ea788 2019-11-04)
binary: rustc
commit-hash: 4560ea788cb760f0a34127156c78e2552949f734
commit-date: 2019-11-04
host: x86_64-apple-darwin
release: 1.39.0
LLVM version: 9.0