I want all side gradient shadow button in swiftUI

I want to achieve this kind of gradient shadow in swiftUI button. Any help or suggetion will be appreciated. I have already achieved gradient border. Thanks in advance!!

You could create custom ButtonStyle implementation of which may look like this one:

struct GradientButtonStyle: ButtonStyle {
    
    private struct GradientButtonPreferenceKey: PreferenceKey {
        static var defaultValue: CGSize = .zero
        
        static func reduce(value: inout CGSize, nextValue: () -> CGSize) { }
    }
    
    @State private var buttonSize: CGSize = .zero
    
    func makeBody(configuration: Configuration) -> some View {
         configuration.label
             .padding()
             .background(.white)
             .clipShape(RoundedRectangle(cornerRadius: 10))
             .overlay {
                 GeometryReader { proxy in
                     Color.clear
                         // Getting current size of button
                         .preference(key: GradientButtonPreferenceKey.self, value: proxy.size)
                 }
             }
             .background {
                 Rectangle()
                 // We'll use Linear gradient with three colors I can see in your example.
                     .fill(LinearGradient(colors: [.yellow, .purple, .blue],
                                          startPoint: .leading,
                                          endPoint: .trailing))
                 // You can adjust gradient size by multilplying its value on desired factor here
                     .frame(width: buttonSize.width, height: buttonSize.height)
                 // Higher the number further from body gradient will be "sprayed".
                     .blur(radius: 30)
                 // Makes cool effect of pressing the button.
                     .opacity(configuration.isPressed ? 0.7 : 1)
             }
             .onPreferenceChange(GradientButtonPreferenceKey.self, perform: { value in
                 buttonSize = value
             })
    }
}

And after usage of the style:

Button("Custom Gradient Button") {}
    .buttonStyle(GradientButtonStyle())

You get the result:

NOTE: Once gradient being blurred it is impossible(at least I don't know the way) to get the frame of the "sprayed" area, so all spacing, padding et cetera. Will be calculated from the body of the button, in this current case – white rectangle.