refactor: refactor load package

[zong-zhe]

1. Does this PR affect any open issues?(Y/N) and add issue references (e.g. "fix #123", "re #123".):

• N
• Y

re #478

2. What is the scope of this PR (e.g. component or file name):

3. Provide a description of the PR(e.g. more details, effects, motivations or doc link):

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Other

4. Are there any breaking changes?(Y/N) and describe the breaking changes(e.g. more details, motivations or doc link):

• N
• Y

5. Are there test cases for these changes?(Y/N) select and add more details, references or doc links:

• Unit test
• Integration test
• Benchmark (add benchmark stats below)
• Manual test (add detailed scripts or steps below)
• Other

[coveralls]

Pull Request Test Coverage Report for Build 10957207940

Details

• 108 of 167 (64.67%) changed or added relevant lines in 5 files are covered.
• 55 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.5%) to 41.674%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/downloader/source.go	0	3	0.0%
pkg/package/package.go	85	141	60.28%

Files with Coverage Reduction	New Missed Lines	%
pkg/package/modfile.go	18	35.8%
pkg/client/client.go	37	56.73%

Totals
Change from base Build 10955213375:	-0.5%
Covered Lines:	3446
Relevant Lines:	8269

---

💛 - Coveralls

[Peefy]

LGTM

[Peefy]

Why change filepath to modfilepath?

[zong-zhe]

fixed