refact: middlewares and 404

[sorrycc]

;;

[coveralls]

Pull Request Test Coverage Report for Build 327

• 0 of 6 (0.0%) changed or added relevant lines in 5 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.2%) to 9.463%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
packages/af-webpack/src/dev.js	0	1	0.0%
packages/umi-plugin-routes/src/index.js	0	1	0.0%
packages/umi-plugin-dll/src/index.js	0	1	0.0%
packages/umi-build-dev/src/UserConfig.js	0	1	0.0%
packages/umi-build-dev/src/Service.js	0	2	0.0%

Files with Coverage Reduction	New Missed Lines	%
packages/umi-plugin-routes/src/index.js	1	0.0%

Totals
Change from base Build 323:	0.2%
Covered Lines:	112
Relevant Lines:	1544

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💛 - Coveralls