map big decimals

Author: HugoMario

src/main/java/io/swagger/codegen/v3/generators/go/AbstractGoCodegen.java

@@ -78,6 +78,7 @@ public AbstractGoCodegen() {
         typeMapping.put("number", "float32");
         typeMapping.put("float", "float32");
         typeMapping.put("double", "float64");
+        typeMapping.put("BigDecimal", "float64");
         typeMapping.put("boolean", "bool");
         typeMapping.put("string", "string");
         typeMapping.put("UUID", "string");