logical error allowing for duplicate species fixed

pkg/country.go

@@ -58,7 +58,7 @@ func GetCountryByCode(code, limit string) (Country, int) {
 		// and checks if the country-code is correct
 		if country.Code == species.Results[i].CountryCode {
 			// and checks that the species is unique
-			if species.Results[i].SpeciesKey != 0 || contains(country.SpeciesKey, species.Results[i].SpeciesKey) {
+			if species.Results[i].SpeciesKey != 0 && contains(country.SpeciesKey, species.Results[i].SpeciesKey) {
 				country.Species = append(country.Species, species.Results[i].Species)
 				country.SpeciesKey = append(country.SpeciesKey, species.Results[i].SpeciesKey)
 			}