chore(travis): support go1.15

[easonlin404]

No description provided.

[codecov]

Codecov Report

Merging #787 into master will decrease coverage by 0.11%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #787      +/-   ##
==========================================
- Coverage   82.32%   82.20%   -0.12%     
==========================================
  Files           8        8              
  Lines        1748     1748              
==========================================
- Hits         1439     1437       -2     
- Misses        192      193       +1     
- Partials      117      118       +1     

Impacted Files	Coverage Δ
parser.go	77.24% <0.00%> (-0.23%)	⬇️

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