fix json unmarshal error when list plguins

[nayihz]

Type of change:

• Bugfix
• New feature provided
• Improve performance
• Backport patches

What this PR does / why we need it:

bug fix #883
the response body is JSON with unknown field names but not a string slice.

Pre-submission checklist:

• Did you explain what problem does this PR solve? Or what new features have been added?
• Have you added corresponding test cases?
• Have you modified the corresponding document?
• Is this PR backward compatible? If it is not backward compatible, please discuss on the mailing list first

[codecov-commenter]

Codecov Report

Merging #888 (4c0ed87) into master (e2475cf) will increase coverage by 0.02%.
The diff coverage is 100.00%.

❗ Current head 4c0ed87 differs from pull request most recent head 1740faf. Consider uploading reports for the commit 1740faf to get more accurate results

@@            Coverage Diff             @@
##           master     #888      +/-   ##
==========================================
+ Coverage   32.01%   32.04%   +0.02%     
==========================================
  Files          70       70              
  Lines        7749     7752       +3     
==========================================
+ Hits         2481     2484       +3     
  Misses       4993     4993              
  Partials      275      275              

Impacted Files	Coverage Δ
pkg/apisix/cluster.go	33.03% <100.00%> (+0.45%)	⬆️

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[tao12345666333]

Thanks! It's on my list

[tokers]

@cmssczy Thanks for your PR, could you give us an example about the response? Fair to say, I didn't realize the difference.

[nayihz]

could you give us an example about the response? Fair to say, I didn't realize the difference.

@tokers
The response body json format is like:

{
	"serverless-pre-function": {
		"version": 0.1,
		"priority": 10000
	},
	"echo": {
		"version": 0.1,
		"priority": 412
	}
}

It is a json struct with unknown field names but not a string slice. So I think we should use a map instead of slice.

[tao12345666333]

LGTM

[lingsamuel]

We need a mechanism to ensure that the APISIX interface we are using is not outdated.

[tao12345666333]

We need a mechanism to ensure that the APISIX interface we are using is not outdated.

yep. we may need to convert directly from the upstream schema.

now let's move forward.