[Development]Met error after executing 'make all'

[jerryion]

Met error after executing 'make all' under main folder.

Expected Behavior

Install dependencies, generated code, and run the app

Current Behavior

Running verify_swagger
panic: Invalid schema provided to SchemaValidator: object has no key "default"

goroutine 1 [running]:
github.com/go-openapi/validate.NewSchemaValidator(0xc0001a26c0, 0x19085a0, 0xc0001a26c0, 0x0, 0x0, 0x1aaa760, 0xc0003bc240, 0x0, 0x0, 0x0, ...)
	/Users/pumpkinyang/go/pkg/mod/github.com/go-openapi/validate@v0.19.2/schema.go:72 +0x1039
github.com/go-openapi/validate.(*SpecValidator).Validate(0xc00015a480, 0x18bbec0, 0xc0003fe050, 0xc000290000, 0xc0002900b0)
	/Users/pumpkinyang/go/pkg/mod/github.com/go-openapi/validate@v0.19.2/spec.go:92 +0x216
github.com/go-swagger/go-swagger/cmd/swagger/commands.(*ValidateSpec).Execute(0xc00046afb0, 0xc00000ff40, 0x1, 0x2, 0xc00046afb0, 0x1)
	/Users/pumpkinyang/go/pkg/mod/github.com/go-swagger/go-swagger@v0.20.1/cmd/swagger/commands/validate.go:60 +0x14e
github.com/jessevdk/go-flags.(*Parser).ParseArgs(0xc000043800, 0xc0000b4190, 0x2, 0x2, 0x0, 0x1957631, 0x2a, 0x17d5540, 0xc00024d950)
	/Users/pumpkinyang/go/pkg/mod/github.com/jessevdk/go-flags@v1.4.0/parser.go:316 +0x8dc
github.com/jessevdk/go-flags.(*Parser).Parse(...)
	/Users/pumpkinyang/go/pkg/mod/github.com/jessevdk/go-flags@v1.4.0/parser.go:186
main.main()
	/Users/pumpkinyang/go/pkg/mod/github.com/go-swagger/go-swagger@v0.20.1/cmd/swagger/swagger.go:145 +0xc2c
make: *** [verify_swagger] Error 2

Possible Solution

Upgrade go-swagger from v0.20.1 to v0.21.0 as follow link described:
go-swagger/go-swagger#2063

Steps to Reproduce (for bugs)

1. go version go1.13.4 darwin/amd64
2. master branch

[zhouzhuojie]

Thanks for reporting!