Update flush, add two return parameters

[wayblink]

/kind improvement

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[mergify[bot]]

@wayblink Please associate the related issue to the body of your Pull Request. (eg. “issue: #187”)

[codecov[bot]]

Codecov Report

Merging #318 (267fc64) into master (a4f6dcc) will not change coverage. The diff coverage is 85.71%.

@@           Coverage Diff           @@
##           master     #318   +/-   ##
=======================================
  Coverage   89.12%   89.12%           
=======================================
  Files          25       25           
  Lines        2740     2740           
=======================================
  Hits         2442     2442           
  Misses        212      212           
  Partials       86       86           

Impacted Files	Coverage Δ
client/client.go	76.31% <ø> (ø)
client/client_grpc_data.go	71.78% <83.33%> (ø)
client/client_grpc_index.go	83.63% <100.00%> (ø)