switch from micro/go-config to spf13/viper

[Ahmed]

For stability & reduce upgrade hurdles, i will switch to spf13/viper

$ go get -u

go: github.com/testcontainers/testcontainer-go@v0.0.2: parsing go.mod: unexpected module path "github.com/testcontainers/testcontainers-go"
go: finding github.com/gregjones/httpcache latest
go: finding github.com/dgryski/go-bitstream latest
go: finding github.com/k0kubun/colorstring latest
go get: error loading module requirements

Currently github.com/micro/go-config face a problem with one of the dependencies chain.